Lower Silurian Fauna of Minnesota. 



343 



Cycloncma scmicarinatum Salter : — The specimens here identified 

 have a small umbilicus but in other respects they are as described and fig- 

 ured by Mr. Salter. (Canadian Organic Remains, Decade I.) 



Holopea perundosa n. sp. — This species has been put among the holo- 

 pea mainly because of its supposed relation to H. pyrene Billings. 



Modiolopsis nicyeri Billings. — The specimens in hand may be M. sit~ 

 perha Hall. 



Tellinomya candens n. sp. has been referred to that genus although 

 the characteristic hinge teeth have not been made out. Perhaps the species 

 belongs more properly to some other genus, as Orthonetella S. A. Miller. 



Crania granulosa N. H. Winchell. — Two specimens only have been 

 found, with the characteristic granulose surface. I am not decided as to 

 whether it is a distinct species or not, although I have satisfied myself that 

 the granulose surface is incidental to decomposition of small shells in the 

 magnesian limestones and shales. Small gastropods and lamellibranchs 

 frequently have the same marking. But in the brachiopoda it is known to 

 me only in these two specimens and may indicate some specific character. 



Streptorhynclnis convexum Owen (1840) is distinguished from S. fil- 

 itexum Hall (1847) by having more nearly the exterior markings of 

 Stropomena altcrnata Con., by a triangular outline, thicker shell, greater 

 convexity, broader hinge proportionally, and smaller size. They are nearly 

 always associated. They are sufficiently distinct for separation although 

 no one characteristic serves as a criterion. 



December 8th, 1891. 



