KONGL. SV. VET. AKADEMIEN8 FIANDLINGAB. BAND 34. n:o 8. 63 



Niobe frontalis Ang. 



IM. V figs. 19—21. 



The pocketlike consoles are shorter and broader than in N. laevicepa and the rna- 

 eulae also larger and of an elliptic shape. In a horizonta] sectkm near the surface the raa- 

 cula has a speckled appearance of black döts, indicating an undeveloped prismatic struc- 

 ture, niuch more primitive than in the Asaphidae. 



Niobe Iffiviceps Ang. 



Pl. V figs. 22—26. 



It differs from the preceding through longer consoles below the maculae, which are 

 oval and in a horizontal section exhibit the same spongious structure, pl. V fig. '!■). The 

 cephalic eyes eonsist of polyedric prisms, which through deterioration show a central 

 cylindrical core surrounded by darkish matter like Asaphus. The passage from solid, 

 homogenous prisms to chamred ones is most evident in the figure 22. 



Ogygia Brongn. 



Fijjures of the maculae are found in 



0. Buchi Salter, Mem. Geol. Surv., Dec. II pl. VI fig. 3 p. 2, where it is stated 

 that »there are two transverse furrows near the apex, with compressed tubercles between 

 them». There are two narrow crescentic maculae and between them a little lower a longer, 

 crescentic ridge, which may be the ridge that in other species conneets the ma-eulae. 

 Moreover, the shape of the hypostoma is not concordant with that of the other species. 

 In Monogr. Brit Trilob. pl. 15 figs. 2, 3 there is only a reproduction of the former figure. 



0. comdensis Murch. Salter in Monogr. pl. 16 fig. 10 interiör side of the hypo- 

 stoma with two lateral maculae. In the description »two pairs of furrows» the uppermost 

 is the maculae; H. Wyatt-Edgell »On the Genera of Trilobites Asaphus and Ogygia and 

 the Subgenus Ptychopyge» in Geol. Magaz. 1867, p. 14, 15 fig. 2 probably a cast with 

 two oblique impressions of maculae. 



0. dilatata (Asaphus) Särs var. Sarsi Ang. Särs in Isis 1835 p. 342, pl. IX fig. 

 11. The figure has two small maculaB near the posterior margin and the author says 

 »mit einer starken Vertiefung öder Einschnitt an jeder Seite des Endes». Angelin pl. 

 XLII tig. 1 6. Brögger's fig. 38 pl. 3, in II, comes near to the specimen, which is de- 

 scribed below, also belonging to Dr. G. Holm. 



0. dilatata var. Sarsi Ang. 

 Pl. V tigs. 27, 28, 



The hypostoma is in so far deviating that the terrace lines have a nearly vertical 

 direction and in this respect niuch resemble those of the Phillipsiae and the Proeti. The 



