BTHANG TILL K. SV. VBT.-AKAB. HANDL. BAND. 3. N:0 12. 21 



ginal umbone, and the ventral valve conical, with excentric um- 

 bone, and perforated by a small round foramen. Acrothele dIfFers, 

 however, at least from the typical species, such as Acrotreta 

 subconica KuT. and A. gemraa Bill., by having the ventral valve 

 much loAver, and the false area only very slightly indicated. 

 More nearly related than the typical species is probably the 

 doubtful Acrotreta Nicholsoni Dav. Among the Russian Bra- 

 chiopoda described by Kutorga ') Siphonotreta tentorium may 

 also be a somewhat allied species. As Kutörga himself remarks, 

 it differs much from the typical Siphonotretce, but also from 

 Acrotreta, by not having any traces of a false area. Like the 

 true Siphonotreta} it is said to have the surface covered with 

 warts and spines. 1 do. not think it improbable that some spe- 

 cies described as Discince will prove to belong to this genus, 

 for in many species the characteristic longitudinal slit in the 

 ventral valve has not been observed. Thus, for instance, I may 

 suppose that the Discina f)rimceva Barr. & Vern. -) is founded 

 on a ventral valve of this genus. 



Acrothele coriacea n. sp. 



Pl. IV, figs. 44—48 (and 49, 50?). 



Almost circular in outline, but a little wider than long, 

 broadly rounded anteriorly, somewhat truncated posteriorly; 

 greatest width usually a little before the middle. Outermost 

 shell layer rough, somewhat like leather, not distinctly granulated, 

 usually of a duU brown or nearly black colour, but in some few 

 Westrogothian specimens bluish. — Ventral valve slightly conical, 

 with the umbone very excentric, its distance from the anterior 

 margin being two or three times that from the posterior. The 

 umbone consists of two very small wart-like protuberances. Close 

 behind the warts the shell is perforated by a foramen which, 

 owing to its extreme minuteness, is usually difficult to discern. 

 Between the umbone and the posterior marojin there is a narrow, 

 triangulär, somewhat flattened space, which might be considered 

 as an indication of a false area. This area is, however, very 

 faintly marked and not sharply separated from the other part of 

 the shell, nor is there any trace of a longitudinal groove as in 



') Ueber die Brachiopoden-Familie der Siphonotretseae, Yerhandl. der Kais. 



Mineral. Gesellpchaft 1847. 

 2) Bull. Soc. Géol. Fr., t. XVII, p. 532, pl. VIII. fig. 4. 



