p 



Ohs. — The central portion of the cephalic shield, or cephalon, 

 is all that is preserved of this interesting crustacean. The reason 

 for separating it from P. australis, Woodw., sp., are the follow- 

 ing : — (1.) Presence of the strong ocular ridges, absent in the 

 latter; (2) direction of the facial sutures, which in P. australis 

 are said to be " somewhat oblique," but here are certainly straight 

 anterior to the ocular ridges, and do not commence near the 

 anterior angle (s) of the glabella; (3) absence of oblique striae in 

 advance of the eyes ; and (4) the position the eyes would occupy 

 were they preserved. As regards the last point of difference in 

 P. australis the anterior ends of the eyes are decidedly well 

 forward, but I believe the corresponding points in P. Hotvchini 

 will be found to be much more posterior in position. In most 

 Ptychoparice possessing ocular ridges, the anterior terminations 

 of the eyes are situated at the distal or posterior ends of the 

 ocular ridges. Now these points in P. Howchini are much more 

 posterior than the corresponding positions in P. australis. Herein, 

 in my opinion, lies a fundamental difference between the two 

 types. 



To Ptychoparia are also referable, in all probability, most, if 

 not all the fragmentary cephalic shields, described by me from 

 Caroline Creek, Tasmania.* 



[The Type specimen is in the Australian Museum, Sydney, 

 presented by Mr. Howchin.] 



EXPLANATION TO PLATE IV. 



Ptychoparia Howchini. 

 Fig. 

 L The cephalon or head shield as far as preserved, front view. 



2. The same, side view. 



3. Granules forming the sculpture, much enlarged. 



Proc. R. Soc. Tas. for 1882 (1883), pp. 153-157. 



