108 INTRODUCTION TO CONCHOLOGY. 



scopic examination, a larger proportion of membranaceous 

 tissue, and less of calcareous matter, than is usually secreted 

 by his brethren, would be discovered. 



The second genus, Stnithiolaria, which inhabits the 

 shores of New Holland, exhibits a strange mollusk, of 

 which the disc is supported on a stout pedicle, with a 

 truncated proboscis-like prolongation of the head, and the 

 absence of a breathing siphon. It seems scarcely possible 

 that such an ungainly and half-formed creature should con- 

 struct for himself a dwelling, however humble, and dwell 

 therein with facilities for enjoyment. Yet such is doubtless 

 the case, for the power of erecting that same dwelling is 

 productive of happiness to its artificer. 



In the animal of the Aporrliais a different structure 

 becomes obvious : the disc is truncated in front, carrying 

 at the extremity a small horny operculum; the head is 

 large, the mouth longitudinal, occupying the lengtli of the 

 truncated portion of the head, and the tentacles long and 

 pointed, pedunculated at the base, at the summit of which 

 singular portion is the eye. 



Such is the formation of this peculiar mollusk, which 

 yet constructs a dwelling somewhat more elaborate than 

 that of liis uncouth brother, having simple or expanded 



