56 



LINDSTRÖM, VISUAL ORGANS OF THE TKILOBITES. 



Encrinurus E 



MMR. 



I cannot find any former figure indicating the maculae 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 lagvis we have found the anterior börder so eharacteristic 

 in them that it is sufficient to distinguish them from each other and to annul the doubts 

 concerning the distinction of Encr. bevis from Encr. punctatus. We therefore in pl. IV 

 tigs. 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 surfaee of the hypostoma is so finely and obscurely granulated that it seems 

 to be almost smooth. It is in the shallow groove above the lamollar tongueshaped pos- 

 terior börder that the elongated tubercular maculae are situated. They are prominent 

 and in horizontal sections they have a surfaee mottled by irregular black and white specks, 

 the whole surrounded by a white börder, fig. 6. This börder and the other surfaee 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 sub- 

 stance on the sides is pierced by the straight, black tubes. 



The cephalic eyes have the prisms indistinctly developed or badly preserved with 

 ;i diameter of 0,04 millim. and height of 0,ot millim. In Encr. bevis the prisms are more 

 distinct and larger with a diameter of 0,oe millim. (pl. IV figs. 10 — 11). 



The maculae are well developed, ovate, in E. bevis 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 

 II. W()()i)\v.\i;i)'s work pl. VI fig. 5 two somewhat obscure macuhe, but no mention is 

 made of them in the description. 



Harpes Gol 



1)F. 



Harpes d' Orbignyanus Barr. Novak II Taf. I fig. 4, with small black macuhe. 

 Harpes venulosus Corda. Novak II, Taf. I figs. 1, 2. Two narrow, horizontaily 

 placed maculae. 



Harpina Barr. 



H. prima Barr. Novak II Taf. I fig. 5- Two maculae in continuation of a nar- 

 row groove, at the base of the central globosity. 



