CAMAROPHORIA. 25 



conjoined at their dorsal margins, forming a trough-shaped process, affixed to a low medio- 

 longitudinal plate (PI. I, figs. 24, 25, 27). In the dorsal valve the space between the 

 sockets is occupied by a small cardinal muscular process or boss, on either side of which 

 are two long, slender, curved processes, and to which were no doubt attached the free 

 cirriated spiral arms : from beneath the cardinal process a high vertical mesial septum 

 extends to a little more than a third of the length of the valve, supporting along and close 

 to its upper edge a spatula-shaped process, considerably dilated towards its free extremity, 

 and projecting with a slight upward curve to nearly the centre of the shell (figs. 15, 26, 27). 

 The vascular markings (figs. 13, 14) have been described by Professor King, as well 

 as in my Introduction, and are beautifully preserved on many examples of the larger 

 species from our Permian beds. 



Camarophoma Schlotheimi, Von Buck, sp. Plate II, figs. 16 — 27; and King's Mon., 



pi. vii, figs. 10 — 21 ; and pi. viii, fig. 8. 



Terebratulites lacunosus (part), Schlotheim. In Dr. Leonhard's Min. Taschenbuch, 



1813. 

 Terebratula Schlotheimi, Von Buck. Ueber Terebrateln, p. 39, pi. ii, fig. 32, 1834. 



This abundant and characteristic species varies less in shape as in the number of its 

 ribs ; is wider than long, and somewhat obscurely rhomboidal or sub-pentagonal, the 

 greatest width being situated at about the anterior portion of the shell. The valves are 

 unequally convex, and possess marginal expansions, which, when fully developed, produce 

 a flattened frill, as wide as half the length and breadth of the shell. The dorsal valve is 

 often gibbous, and presents in profile a convex arch, with its marginal expansions slightly 

 bent upwards. The mesial fold differs in width and elevation, according to the number of 

 ribs which ornament its surface, these varying from two to seven in different ages and 

 individuals. On the lateral portion of the valves the ribs are also at times obscurely 

 defined, and vary in number from two to six on either side. The ventral valve is most 

 convex about the beak, this last being small, slightly produced, and incurved, so that the 

 deltidial plates which margin the foramen are but rarely exposed, except in very young 

 individuals : the beak ridges are also but slightly defined ; the sinus is of greater or lesser 

 depth, and ornamented by from one to five ribs, which first appear at about the middle 

 of the shell, and extend thence to the front. Shell-structure not perforated. 1 The 

 measurement, taken from a specimen with its marginal expansions fully developed, offered 



1 In page 117 of bis Monograph of ' English Permian Fossils,' Professor King describes the shell- 

 texture of Camarophoria as possessing extremely minute punctures, but Dr. Carpenter could find none, 

 and pronounced the genus and present species to be "not perforated," at p. 35 of our General 

 Introduction. 



4 



