71 



so that further investigation may not unlikely prove them 

 distinct. Mr. May is endeavouring to obtain some fresh 

 material. Then, again, I have a single shell that I collected 

 at Port Lincoln, which is strongly carinated, but otherwise 

 both in girdle and sculpture approaches the Tasmanian shells, 

 and in this specimen also there is no evidence of the strange 

 oar-headed spicules. 



Family MOPALIIDAE, Pilsbry. 



Kopionella, n. gen. 

 Differs from Plaxiphora, Gray — 



(1) In having peculiar oar-headed girdle bristles or 

 spicules. 



(2) In having an elevated, recurved tail valve with 

 terminal mucro. 



(3) The minor differences detailed hereunder. 

 Differs from Frembleyana, H. Ad. 



(1) In having peculiar oar-headed bristles or spicules. 



(2) In the slits in the median valves being centrally 



situated and sinus, especially in tail valve, being 

 much narrower. 



(3) The minor characters detailed below. 



Type. — Plaxiphora matthewsi, Iredale. The specimen 

 described herein is being presented to the South Australian 

 Museum. 



Description and comparisons, of further differences. — For 

 purposes of this comparison Plaxiphora albida is used as 

 typical of the genus Plaxiphora. In P. matthewsi, Ire., the 

 upper side of the tail valve is very distinct from P. albida, 

 Blain., in that the anterior and posterior margins of the 

 tegmentum are so folded over as to form strongly-raised ribs ; 

 the mucro is terminal, much raised, and slightly recurved, as 

 in Loricella. Inside the sinus is comparatively narrow and 

 deep, whereas in Plaxiphora the sinus is wide. In the median 

 valves of P. matthewsi the tegmentum of the upper-side is 

 folded over to the inside, and forms there a strongly-raised 

 rib, extending from side to side ; in the anterior valve this 

 folding forms a still deeper and sharper ridge. While there 

 is the infolding in the Plaxiphora, this characteristic ridge is 

 not formed. The teeth of the anterior valve are much more 

 cleanly cut and less clumsy and thick than is the case in the 

 Plaxiphora. The slits in the median valves show a striking 

 feature in that that portion abutting on the slit is carried 

 upwards under the eaves in two pillars. 



