330 PLAXIPHORA. 



P. OBTECTA Carpenter, n. sp. 



Shell large, broad, partly covered. Valves smooth, most minutely 

 punctulate angulate in front ; sutural sinus large, produced forward 

 over the jugum ; lateral areas scarcely defined except by an angle 

 at the forward outer margin of the valves ; dorsal ridge rounded. 

 Intense olivaceous, paler on the dorsal ridge. Mucro of posterior 

 valve terminal hardly produced. 



Interior : posterior valve with flattened insertion-plates. Anterior 

 valve with 8, central valves 1 slit ; teeth very acute, long, smooth, 

 a little thickened at the slit-edges ; eaves narrow, spongy. Sinus 

 deep, very obtusely angular, with a spongy area. Sutural laminae 

 long, separated. Girdle very broad, sinuated behind, with bundles 

 of about three large, horn-like hairs at the sutures, and having 

 smaller ones sparsely scattered all over more or less closely. ( Opr.} 



Length 50, breadth 32 mill.; divergence 120. 



New Zealand (Mus. Cum., no. 45.) 



This very interesting shell differs from the typical Plaxiphorw as 

 Fanneltia does from Tonicia. It is, however, simply an exaggera- 

 tion of P. terminalis. 



Section Fremblya H. Adams, 1866. 



Frembleya H. AD., P. Z. S. 1866, p. 445. Type F. egregia H. 

 AD. Fremblya CPU., MS. and in Proc. U. S. Nat. Mus. 1881, p. 284. 

 Streptochiton CPR., MS. olim. 



Shell and girdle like Plaxiphora except that the former is short and 

 broad, the tail valve very much reduced in size, strongly arched 

 upward in the middle behind. Slits in intermediate valves poste- 

 riorly situated. Girdle having more or less obvious sutural pores. 



The sculpture of these forms is like that of the more elaborately 

 carved Plaxiphoras of the same regions; but the considerable 

 modification in the general form of the tail valve may be held to be 

 sufficient ground for the retention of Adams' generic name in a sec- 

 tional sense. The organization throughout is otherwise very similar 

 to that of Plaxiphora. Two species only are known : P. egrcgia, in 

 which the shell is of a peculiar cg.ir shape, wider behind the middle, 

 and the insertion plates are much thickened outside at the edges of 

 the slits, and P. ovata, in which the shell is widest at the fourth 

 valve, rapidly narrowing toward both ends. 



The following description of his new genus is given by H. Adams : 



