MORRISIA. 



579 



longitudinally depressed, Internal skeleton consisting of a 

 small forked process arising from the septum near the centre 

 of the valve. 



Ex. K. Lamarckiana, Davidson, pi. 131, fig. 4. Shell, 

 K. pisum, Valenciennes, fig. 4, a, 4, b. 



The inferior peduncle muscles in this genus are large, and 

 leave two wide impressions close to the hinge. The mesial 

 ridge or septum extends to ahout half the length of the dorsal 

 valve, and the two small forked lamellae which arise from 

 its extremity diverge and are expanded at their ends. 



Species of Kraussia. 



Caipensis, Adams and Reeve. pisum, Lam. 



cognata, Chem. rubra, Pallas. 



Lamarckiana, Davidson. 



Genus MORRISIA, Davidson. 



Shell coarsely punctate, with a large foramen encroach- 

 ing equally on both valves ; ventral valve with a small 

 straight area. Loop not reflected, united to a small forked 

 process in the centre of the valve. 



Ex. M. anomioides, Scacchi, pi. 131, fig. 5. Shell, M. 

 anomioides, fig. 5, a, 5, b. 



The animal of Morrisia is furnished with two sub-spiral 

 or sigmoid arms with comparatively large cirrhi, which, sup- 

 ported by the crural processes, pass forwards and, converging 

 in front of the mouth, again turn outwards. The shell is 

 minute, circular, and depressed; the deltidia are very small 

 and widely separated; the dorsal or smaller valve is deeply 

 notched at the umbo ; and the apophysary system consists of 



