CAMAROPHORIA 173 



valve. Internally a median septum, thinner and weaker than that of the 

 pedicle valve extends anteriorly from the beak, and supports both the 

 cruralium and the hinge-plate. 



The surface markings of the shell consist of rather strong, more or 

 less regularly arranged concentric lines of growth. 



FIG. 3. A series of five cross-sections of the rostral portion of the shell of 

 Camarophoria Msinuata (X 



Remarks. This species was originally described as a member of the 

 genus Seminula, now known under the name Composita, and in its gen- 

 eral form it does resemble members of that genus. Some examples, even 

 closely resemble small specimens of C. trinuclea, and under certain con- 

 ditions of preservation it might be difficult to separate the forms, but 

 internally the two shells are fundamentally different, the median septum 

 and spondylium being entirely wanting in Composita. The only other 

 species of Cam,arophoria with which it is necessary to compare this one is 

 C. explanata. The more globular examples of C. bisinuata most closely 

 resemble C. explanata, but they may always be distinguished by the 

 absence of any plications upon the lateral slopes of the valves. 



Horizon. Fern Glen formation and lower Burlington limestone. 



CAMAROPHORIA EXPLANATA (McChesney) 

 Plate XXIII, Figs. 46-51 



1860. Rhynchonella explanata McChesney, Desc. New Pal. Foss., p. 50. 

 1865. Rhynchonella explanata McChesney, Plates 111. New Spec. Foss., pi. 



6, figs. 7a-c. 

 1868. Rhynchonella explanata McChesney, Trans. Chicago Acad. Sci., vol. 



1, p. 30, pi. 6, figs. 7a-c. 



1894. Pugnax explanatus Hall and Clarke, Int. to Study of Bra,ch., pt. 2, 



pi. 44, figs. 14-16. 



1895. Pugnax explanatus Hall and Clarke, Pal. N. Y., vol. 8, pt. 2, pi. 60, 



figs. 43-45. 

 1897. Camarophoria explanata Schuchert, Bull. U. S. Geol. Survey No. 87. 



p. 162. 

 3910. Cama-rophoria- explanata Weller, Bull. Geol. Soc. Am., vol. 21, p. 



501, fig. 3. 



Description. Shell small, subglobular in form, usually a little wider 

 than long. The dimensions of the type specimen, which is a little above 

 the average size, are: length 8 mm., width 8.9 mm., thickness 7.5 mm. 

 One of the largest examples observed has a length of 10 mm., but the 



