196 MVALVES. 



The name Pinna, which is sometimes spelled 

 with one n, is supposed to be derived from nuo<; 

 (pinos) the dirt or mud ; but the name given it 

 by British conchologists would lead us to take 

 its derivation from the Latin, pinna, a large 

 feather. 



PINNA Pectinate.* 



SPINY SEA WING. 



Specific Character. Shell triangular, oblong, 

 with about eleven longitudinal ribs, having con- 

 cave spines, which increase in size as they 

 approach the broadest end ; the other side desti- 

 tute of ribs, but obliquely striated ; shell thin, 

 pellucid, brittle, of a light brown colour, darker 

 towards the beaks ; inside of a pearly hue ; 

 breadth three inches at the gaping end, which 

 is slightly rounded ; length six inches and a 

 half. This shell inhabits India ; it has also been 

 found on the coasts of Dorset and Sussex. 



QUESTIONS ON THE BIVALVE 

 SHELLS. 



1. Describe the part of a Bivalve shell which 

 unites the two valves. 



2. By what means are the animals able to 

 open these valves ? 



* Plate X. figure 4. 



