74 PROCEEDINGS OF THE ACADEMY OF 



to make about one turn, beyond which the body part expands 

 very rapidly to the aperture, making less than half of another 

 volution ; aperture proportionally very large, and nearly circular; 

 lip not sinuous or undulated, but sometimes slightly, and broadly 

 retreating behind ; surface without plications or costfB, but thickly 

 covered by numerous slender, tubular spines, which leave small, 

 depressed, smooth, undefined tubercles on the internal cast. 



Length, measuring direct from the most prominent part of the 

 spire to the anterior margin of the aperture, 3.33 inches ; height, 

 to the most elevated part of the dorsal surface, when the shell is 

 placed with its aperture downward, 1.44 inches; length and 

 breadth of aperture, each about 2.90 inches. 



This fine species differs from P. dumosxim^ Conrad, not onl}^ in 

 its much larger size, more oblique, depressed, and more rapidly 

 expanding form, but in having more numerous spines. The largest 

 specimens of that species are said to have more than one hundred 

 spines, while that under consideration must have had more than 

 two hundred. It likewise differs in not having its lip waved or 

 undulated as in Mr. Conrad's species. 



It is probably more nearl}^ related to P. echinatum, Hall, from 

 the Hamilton group. No figures of that species have yet been 

 published, but judging fi'om the description, our shell is not only 

 very much larger (that species being described as from one inch 

 to one and a quarter inch in length, with an aperture one inch 

 in diameter), but wants the sinuous peristome mentioned in the 

 description of P. echinatum. The term " strong nodes" would 

 also not apply to the numerous small obscure elevations marking 

 the positions of the spines on internal casts of our species. 



None of our specimens show the entire length of the spines, 

 but judging from the fact that their broken ends, at a distance of 

 0.42 inch from their bases, only measure 0.08 inch in diameter, 

 they would seem to have been probably shorter and more slender, 

 as well as much more numerous, than those of P. dumosum. Al- 

 though these spines are as completely tubular as those of the 

 genus Productus, their internal cavitj^ does not seem to have 

 communicated with the interior of the shell, with probably the 

 exception of those near the lip ; for if that had been the case, the 

 smoothly rounded obscure tubercles seen on the internal cast 

 would have shown the broken bases of the casts of the internal 

 cavities of the spines. 



[June 6, 



