Part 14

A specimen from Öland has the maculæ lying in the large field of terrace lines above the smooth zone at the posterior margin of the hypostoma. They are larger than in the former species, pearshaped, smooth and no structure visible.

=Encrinurus= EMMR.

I cannot find any former figure indicating the maculæ of the hypostoma in this genus than the only one of ANGELIN, Pal. Scand. pl. IV fig. 6.

As to the shape of the singularly formed hypostoma in the three Swedish species Encr. punctatus, obtusus and lævis we have found the anterior border so characteristic in them that it is sufficient to distinguish them from each other and to annul the doubts concerning the distinction of Encr. lævis from Encr. punctatus. We therefore in pl. IV figs. 12-17 give the anterior margins of these three species, along with the profiles.

Encrin. punctatus WAHLENBERG.

Pl. IV figs. 5-9, 12, 13.

The surface of the hypostoma is so finely and obscurely granulated that it seems to be almost smooth. It is in the shallow groove above the lamellar tongueshaped posterior border that the elongated tubercular macula are situated. They are prominent and in horizontal sections they have a surface mottled by irregular black and white specks, the whole surrounded by a white border, fig. 6. This border and the other surface is pierced by series of parallel slitlike pores, fig. 7, a feature peculiar to this genus. The vertical sections indicate a chain of indistinct prisms with a black, rounded central hollow between thick strata of clear whitish shell substance, figs. 8, 9. The shell substance on the sides is pierced by the straight, black tubes.

The cephalic eyes have the prisms indistinctly developed or badly preserved with a diameter of 0,04 millim. and height of 0,07 millim. In Encr. lævis the prisms are more distinct and larger with a diameter of 0,00 millim. (pl. IV figs. 10-11).

The maculæ are well developed, ovate, in E. lævis and obtusus and in the same position as in E. punctatus.

=Griffithides= PORTLOCK.

The hypostoma of Griff. globiceps PHILL. shows according to the figure given in H. WOODWARD'S work pl. VI fig. 5 two somewhat obscure maculæ, but no mention is made of them in the description.

=Harpes= GOLDF.

Harpes d'Orbignyanus BARR. NOVÁK II Taf. I fig. 4, with small black maculæ. Harpes venulosus CORDA. NOVÁK II, Taf. I figs. 1, 2. Two narrow, horizontally placed maculæ.

=Harpina= BARR.

H. prima BARR. NOVÁK II Taf. I fig. 5. Two maculæ in continuation of a narrow groove, at the base of the central globosity.

=Holmia= WALCOTT.

Holmia Lundgreni MOBERG, Sveriges äldsta trilobiter, Tafl. 14, fig. 10, 11, 12. The maculæ are much prominent and tubercular, elongate narrow, oblique but not mentioned in the description. Hypostoma probably belonging to the terrace-line group. As well seen in original specimens and in the figures in Dr. HOLM'S paper on Olenellus (Holmia) Kjerulfi there are also in this species two distinct macula; near the posterior margin of the hypostoma, above the marginal groove.

=Homalonotus= KÖNIG.

Maculæ have been previously observed in the following species.

Hom. delphinocephalus GREEN, HALL Pal. N. York vol. II pl. 68 fig. 11, incomplete figure with two well marked tubercular maculæ. No description.

=Hom. Knighti= KÖNIG. SALTER II, pl. 12 fig. 10. Maculæ well expressed as oblique tubercles. On page 120 it is said »with a pair of lateral tubercles well developed (as in Asaphus ...)».

This species is identical with ANGELIN'S Homalon. rhinotropis, Pal. Sc., pl. XX fig. 1 e and his figure has two hollow maculæ seen from the inside of the hypostoma.

=Homalonotus Knighti= KÖNIG (= Homal. rhinotropis ANGELIN).

Pl. IV figs. 20, 21.

The maculæ lie as oblong, smooth tubercles surrounded by the irregularly grown granules of the surface, just below the central globosity of the hypostoma. In a preparation from the interior surface of the macula, as seen in transmitted light, fig. 21, this is white with only a few grey spots and on the superior border black streaks, lying obliquely. The substance of the shell around the macula is perforated by the minutest pores amongst which a few larger are intermingled. The granules are also perforated as those in Calymmene and the tubes continue through the shell, visible by their black colour.

=Hysterolenus= MOBERG.

Hyst. Törnquisti MBG., En trilobit från Dictyograptusskiffern p. 320. In the descriptive letter-press, there is said, that in the exterior (lateral) parts of the anterior groove of the hypostoma a distinct tubercle is to be seen on each side. But none of the figures given, Pl. 17 figs. 6, 7, shows them or at least very indistinctly.

=Illænus= DALMAN.