80 



SHELL GALLERY. 



curved plates on the brachial and a ridge on the peduncle valve, 

 is found on the American coast of the Pacific, and in the Atlantic. 



Order 2. — Neotremata, The Discinidce, includes two genera, 

 Discina and Discinisca (Fig. 7), with orbicular conical shells, of 

 horny calcareous composition ; both valves are conical in the former 



Fio-. 7. 



Discinisca lamellosa. Peru. (After Gr. Sowerby.) 



A group of old and young specimens; largest showing foramen in peduncle 

 valve, the rest showing brachial valves. 



genus, but in the latter the peduncle valve is flattened. Sometimes 

 the embryos settle down on the parent shells, and we see a mass of 

 shells in various stages of growth, as in the specimen of Discinisca 

 lamellosa from Peru. 



The CraniidcB form small limpet-like shells (Fig. 8) closely 

 adherent to the rocks by the whole surface of the peduncle valve ; 



Fig. 8. 



Three specimens of Crania anomala on a stone. Loch Fyne. 



although this valve is so named, no peduncle or foramen is found in 

 this family. The Neotremata, like the Lingulidce; are remarkable 



