Part 19

=Phillipsia= PORTLOCK.

DE KONINCK figured a hypostoma of Phillipsia in his »Description des Animaux Foss. de Belgique» as Cyclus Brongniartianus pl. LII fig. J and NOVÁK in III figs. 6, 7 copied it and corrected the error. It is provided with two globular maculæ united by a curved ridge.

Phillipsia Eichwaldi WOODW. NOVÁK III fig. 5 a hypostoma with globular maculæ. We have been able to examine three different, unnamed or undeterminated species, which we distinguish by numbering them.

Phill. No. 1 from the Keokuk group of Crawfordsville, N. America. The hypostoma is broader than in the other species. The nearly horizontal elongated maculæ placed near the median line, close to the lateral margins.

Phill. No. 2 (pl. VI, figs. 15-18) probably from the Carboniferous formation of Belgium is of a lengthened form. The elliptic maculæ in the groove, below the central elevation. They are smooth and surrounded by a flat border.

The cephalic eyes are much destroyed, but seem to have consisted of somewhat semi-prismatic lenses or prisms of the same type as Dysplanus.

Phillipsia No. 3 (pl. VI figs. 12-14) from the Carboniferous strata of Beeren Eiland communicated by Hr J. G. ANDERSSON. It comes near the preceding, is lengthened, but has broader and shorter anterior wings and the inferior surface just above the posterior border peculiarly pitted. The macula lying above this pitted field are ovate. The lenses of the cephalic eye are hemispheric on the surface.

=Platymetopus= ANGELIN.

=Pl. planifrons= ANGELIN.

Pl. IV figs. 50, 51.

This genus may well be kept distinguished from Lichas in consequence of its peculiar hypostoma and its still more peculiar maculæ, not to remind of the other deviating features. The maculæ lie at the end of narrow, sigmoid grooves of their own above the long transverse groove, separating the posterior border from the anterior elevated moiety. They are elongated, curved and entirely covered with a great number of irregular lenticles, translucent through the thin covering membrane.

=Pliomera= ANG.

Pliomera Törnquisti HOLM in Trilobit. Dalecarliens p. 5 fig. 2.

While Pl. Fischeri and Pl. actinura not have any hypostomic maculæ, this species, which Dr. HOLM with some doubt joins in the same genus, has a hypostoma, which as to its general shape resembles that of both the mentioned species, evenly rounded at its posterior border, with a shallow groove encircling the central field. A little below the horizontal diameter of this the maculæ stretch obliquely inwards and downwards. They rest on a little elevation and are elongate, anteriorly acuminated. The figure on HOLM'S plate does not show the maculæ.

=Proetus= STEININGER.

There are some indistinct indications of maculæ in several of the hypostomas figured in BARRANDE'S Système pl. 15.

Proet. signatus LINDSTR., Gotl. Trilob. Pl. XV fig. 17, shows very distinctly the two maculæ.

=Proet. concinnus= DALM.

Pl. VI figs. 19-23.

In this, as well as in the few other species of Proetus which we have studied, there is that peculiarity of the surface of the hypostoma that two more or less distinct ridges form an acute angle just below the faintly arcuated anterior border. The terrace lines are exactly alike those of the Phillipsiæ, only visible on the central field and ceasing just above the maculæ, where there is a transverse smooth field. The posterior margin has two pair of very short points, one on each side. The macula are lengthened tubercles, somewhat bent and have an oblique position. They are surrounded by tiny prickles and as seen in fig. 23 the macula proper forms a white, elliptic spot on the tubercle. The cephalic eyes are lengthened prisms covered by a thick membrane. They are convex at their base and in a transverse section they show a radiate structure of their interior.

Proet. conspersus ANGELIN.

Pl. VI figs. 24-26.

We have figured a decorticated hypostoma with impressions of two reniform maculæ. The vertical sections of the cephalic eyes show a thin stratum where the lenses are much shorter than in the previous species and covered by a thin film of the common test. The same is also the case in a species which probably is Proet. verrucosus.

Proet. signatus LINDSTRÖM.

Pl. VI figs. 27-30.

On the lateral borders of the hypostoma there are short spines, two on each side, but they are placed differently on the specimens and even wanting in some. The elongated, elliptical maculæ bear in their lower end a white spot on which is seen a little cluster of a varying number of small, segregated ocelli, from three to five, according to the different specimens, like so many black points. The maculæ attain the exceptional length of 4,7 millim. in some specimens, but commonly only 2 millim. We have as yet not been able to detect these remarkable ocelli in any other species of Proetus.

Ptychoparia CORDA.

WALCOTT in »Palæontology of the Eureka District», gives on plate X fig. 21 a representation of a hypostoma which near the posterior margin shows two maculæ as narrow, crescentlike ridges and above them two longer and thicker ridges directed obliquely toward the central axis of the hypostoma.