A New Genus of Cambrian Pteropods. 149 



VI. A New Genus of Cambrian Pteropods. 



By G. F. Matthew. 



The hyolithoid pteropods of the St. John group present 

 several different types of structure, of which, perhaps, the most 

 interesting and instructive, as regards genetic relationship, is 

 the one I propose herein to describe. 



In the investigation of some points of structure in these species 

 of pteropods, the writer has been favoured with the assistance 

 and advice of Prof. Alpheus Hyatt, of Boston, a gentleman who 

 lias given much time to the investigation of the structure and 

 affinities of the Cephalopoda, and is, therefore, well qualified to 

 -define the relationship of that class of animals to the pteropods in 

 question. Professor Hyatt's conclusions, after an examination 

 of these fossils, is that they are not Orthocerata, but are pteropods 

 allied to Hyolithes, though with the unusual feature of transverse 

 septa shutting off chambers at the bottom of the tube. Since 

 they were submitted to Professor Hyatt, other individuals 

 of some of the species have been obtained, which exhibit an 

 -earlier or larval condition, represented by a narrow tube, 

 which is analogous to the embryonic or larval tube or prosiphon 

 of the Cephalopoda, as described by several authors. The 

 simple camerated species I propose to describe, under the name of 

 Camerotheca. 



Slender oval or transversely oval cones with attenuated 

 ■apices. In the lower (smaller) part °f ^ ie tube, or coney 

 there are septa that divide off segments of the tube from 

 the body cavity (chamber of habitation). In most species, this 

 septate portion of the cone is prolonged towards the apex into a 

 narrow attenuated tubule formed during the earliest stage of 

 cjroicth ; the tubule is divided by transverse diaphragms (J) at 

 regular intervals, and is more or less flexible. 



In these shells there is added to the ordinary body cavity of 

 Hyolithes, two spaces or regions showing antecedent conditions 

 differing from that manifested by the ordinary thecoid pteropod of 

 the Cambrian and Silurian systems. The first may be designed as 

 the larval region, and is, perhaps, most instructively exhibited in 

 a species (Diplotheca hyattiana, n. gen. et sp.,) which from its 

 subsequent development falls in another genus. The tubule in this 



