324 PLAXIPHORA. 



1867, p. 224. Euplaciphora modesta CPR., MS. 



The sinus is squared, and the internal layer is bevelled off expos- 

 ing the very porous outer layer as in Nuttallina. Back of this 

 porous area, the width of which varies, the surface shows transverse 

 cuts or puncture-slits. The hairs of the girdle show no trace what- 

 ever of arrangement in tufts or pores. The exterior is finely sculpt- 

 ured with zigzag wrinkles, and the diagonal riblets on each valve, 

 as well as the radii on the head valve, may be either nearly smooth 

 or closely granose. The pattern of coloring is characteristic but 

 still quite variable. 



Var. CONSPERSA Adams & Angas. 



Shell oval, little elevated, with obtuse dorsal ridge. Ashy, with 

 a few scattered clouds of dark and olivaceous. 



Valves squared, thin ; apices not conspicuous, jugal areas marked 

 off by slight indentations which are slightly divergent; but other- 

 wise finely sculptured like the rest of the middle part of the central 

 areas ; pleura having about 20 irregularly roughened line on each 

 side, the lirse mainly forming right angles with the diagonal rib, but 

 branching and minutely undulating ; becoming very fine toward and 

 upon the jugum ; interstices very small. Lateral areas with the 

 diagonal rib much elevated, rendered nodulous by the wrinkles pass- 

 ing over it ; the same sculpture extending across the lateral areas 

 and becoming more nodulous at the suture. Anterior valve having 

 8 ribs, besides those at the sutures. Posterior valve having the 

 mucro at the posterior fourth, and with two diagonal ribs. 



Interior : anterior valve having 8 slits, median valves 1 slit, corre- 

 sponding to the external ribs ; the teeth slightly thickened at the 

 edges of the slits. The posterior valve has well developed, sharp 

 insertion-plates on each side. 



Girdle pale brown, maculated with black-brown ; bearing fine, 

 sparsely scattered soft corneous hairs. 



Length 21-22, breadth 12-14 mill., divergence 117. 



Port Lincoln, South Australia, under rocks (Angas.) 



Chcetopleura conspersa AD. & ANG., P. Z. S. 1864, p. 193. 

 ANGAS, P. Z. S. 1865, p. 187. Placiphora conspersa CPR., MS. 



I have seen no specimens of this form, which Carpenter believed 

 to be a variety of P. petholata. The above description is from Car- 

 penter's MS., and was drawn from Angas' type. 



