164 TWENTIETH REPORT ON THE STATE CABINET. 



to include the genera above enumerated, as well as the Genus Camaro- 

 PHORIA, and probably Triplesia and some of the species of Camarella*, 

 and perhaps also the Genus Gyptdia of Dalman, making G. conchydium 

 the tjpet. In this arrangement, it appears to me that we have a well-marked 

 family of Brachiopoda which has existed from the earliest palaeozoic 

 epoch, and has continued throughout the entire series to its close. 



Under the Genus Pentamerella are placed P. araia ( = Fentamerus 

 aratus), P. papilionensis {z=. Pentamerus papilionensis), P. micula (n. s.), 

 P.obsolescens (n. s.), and P. dubia {= Spirifer dubius, Hall, Thirteenth 

 Report on the State Cabinet). 



The Genus Gypidula includes G. occidentalis ( = Pentamerus occiden- 

 talism Hall, Geol. Report of Iowa), and G. Iceviuscula ( n. s.). 



The term Amphigenia is proposed to include the original Pentamerus 

 dongatus of Yanuxem, which possesses characters unlike any other genus 

 of the pentameroid family ; the A. elongata^ and a variety undulata. The 

 species formerly described as subtrigonalis appears to be only a variety of 

 the A. elongata. 



The Genus Renssel^ria is recognized with doubt, and a single species, 

 R. ? johanni, is noticed from rocks of the age of the Upper Helderberg 

 group in Iowa. 



The Genus Terebratula is recognized in the following species : 

 T. lens, T. sullivanti ( n. s.), T. harmonia ( n. s.), T. rcemingeri, T. elia (n. s.), 

 T. jucunda (n. s.), T. navicella (n. s.), T. sirnulator (n. s.). 



It has been found necessary to preserve the generic term Cryptonella 

 for some of the species originally placed under that genus, as will be seen 

 from the following citation, pages 392 and 393 of the volume. 



GENUS CRYPTONELLA (Hall, 1861). 



Shells equilateral, inequivalve, elongate, oval or ovoid ; valves unequally 

 convex, without median fold or sinus, or with this character moderately 

 developed and principally towards the b.ase of the shell. Ventral valve 

 with beak extended or incurved, perforate ; foramen terminal, the lower 

 side formed by two small triangular deltidial pieces, or, in their absence, 

 by the umbo of the opposite valve. Shell-structure finely punctate. Sur- 

 face smooth, or with concentric striae. Valves articulating by teeth and 

 sockets, the dental lamellas of the ventral valve extending downwards 

 into the cavity of the shell. The muscular impressions in the dorsal 

 valve are strongly marked above, and extend in two narrow separated 

 impressions more than halfway to the front of the shell : the ventral 

 cast shows elongated muscular and vascular impressions. 



* I cannot recognize the rhynchonelloid typical species of Camareli,a as congeneric with many 

 of those more recently placed under that genus by its author, 



t In the revision of the Pentameridje, I am by no means sure that the Genus Gyptdta will not 

 be recognized. I have under consideration at the present time an American species of similar external 

 character, presenting certain modifications of the hinge-plate in the dorsal valve, which will require 

 a distinct designation. 



