DESCRIPTION 



OF A 



NEW SPECIES OF PINNOTERES FROM 

 PLACUNA PLACENTA, 



WITH A NOTE ON THE GENUS, 



BY 



JAMES HORNELL, F.L.S., 



AND 



T. SOUTHWELL, A.R.C.Sc, F.L.S. 



[With One Plate.] 



The material upon which the following desciiption is based was obtained during a 

 biological survey of the coast of Okhamandal in Kattiawar. The bays on the north- 

 east seaboard of this district have a bottom composed of extremely soft mud, 

 constituting an agreeable habitat for the window-pane oyster {Placuna placenta), 

 which exists there in extensive beds. During the dissection of numerous individuals 

 of this mollusc, large pea- crabs were found in nearly all cases. The large individual 

 size, greatly flattened appearance, and preponderance in number of the males at 

 once arrested attention as being conspicuously different from any species previously 

 met with by the observer. Later research confirmed the original impression that this 

 form of Pinnoteres constitutes a new species ; on account of the particular habitat 

 wherein it is found the specific name placunce has been considered appropriate. 



The detailed description of the two sexes is as follows : — 



Pinnoteres placunse, n. sp. 



Female. — Body soft and membraneous ; carapace broader than long, circular in 

 outline, smooth and greatly flattened dorso-ventrally ; lateral margins entire ; front 

 broad, sharply truncated, and straight. Eyes, eye-stalks, and the whole of the orbit 



