62 CONTRIBUTIONS 



lanceolate, excavated, escutcheon long and excavated ; 

 nymph small and deeply seated ; teeth small ; anterior 

 and posterior cicatrices placed on a raised seat ; palleal 

 cicatrix passing between the two great cicatrices in a gen- 

 tle curve ; margin crenulate. 

 Diam. .4, Length .7, Breadth .9, of an inch. 



Observations. This interesting and remarkable species 

 cannot easily be confounded with any other with which I 

 am acquainted, except that which follows. Its oval form, 

 flat beaks and large transverse folds or ribs, are remark- 

 able. 



In dedicating it to my friend, P. H. Nicklin, I have 

 great pleasure in acknowledging my obligations to him, 

 for his kind assistance in occasional difficult points. 



A. sulcata. Plate 2. Fig. 36. 



Description. This species is so precisely similar to the 

 last, with the exception of a marginal furrow, that I 

 have thought it unnecessary to recapitulate the descrip- 

 tion. The Nicklinii is beautifully crenulate on the margin, 

 while the sulcata is furnished with a margin, along whose 

 inner edge a perfect furrow passes from the anterior to the 

 posterior part of the hinge. When very young the speci- 

 mens are almost perfectly flat, and might, for this reason, 

 easily be taken for a different species. 



