52 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Caprinella. — In Caprinella both valves are tubular; indeed the shell 

 is made up of tubes, the inner layer being evanescent, whilst the sur- 

 face is formed by an extremely thin compact lamina. That the tubes 



Figs. 23, 24.- 



-Sections q/Caprinula Boissii, jyOrb. 

 Chalk near Lisbon (Mr. D. Sharpe). 



From Lower 



Fig. 23. 



Fig. 24. 



Fig. 23. (A) Transverse section of straight valve. 



Fig. 24. (B) Transverse section of spiral valve of a w^eathered specimen which has 



lost the outer layer : /, I, position of ligamental inflection ; t, t, teeth ; 



c, c, cartilage-pits ; u, u, urabonal cavity. 



were open is proved by the limestone and small shells contained in 

 them ; and it is very improbable that even in the lifetime of the animal 

 they were permanently occupied by processes of the mantle. They are 

 rather to be compared to the tubular ribs of Cardiwn costatum, 

 which remain open, simply because the animal does not secrete suffi- 

 cient lime to render them solid. 



Figs. 25, 26, 27. — Caprinella triangularis, Desm. f nat. size. 

 From the Upper Greensand of Rochelle. 



Fig. 25. 



Fig. 25. (A) Portion of the left valve, after D'Orbigny ; the shell- wall has been 

 removed by weathering, and the camerated interior exposed. 



Fig. 26. (B) Mould of five of the water-chambers. 



Fig. 27. (C) Mould of the body-chamber : u, right umbo ; s, left umbo ; t, dental 

 groove ; a, surface from which the posterior lobe has been detached. 



