with a revision of the Limnceidce of Authors. 335 



The authors state that this differs from the last species, in 

 being thinner and smaller, in the spire being more elevated and 

 the aperture being less produced in front. It has not b:en 

 fio-ured, and no specimens have as yet reached this country. 



Poilipliolyx, var. solida, Dall. 



The specimens received from Clear Lake through Mr. liar- 

 ford differ essentially from authentic specimens of P. effusa. 

 The shells, when compared with the last mentioned species, 

 differ in the following particulars : 



The most noticeable difference is in the spire. In P. effusa 

 it is nearly flat, so that the shell may be laid down upon the 

 apex without falling to one side. In the species under con- 

 sideration, the spire is elevated, the whorls are rounded below 

 and slightly appressed against the suture, while in P. efusa 

 they are not appressed. The apex of my specimens is more 

 prominent than that of P. effusa, the shells are much more solid 

 and strong. The last whorl of P. effusa is much larger, pro- 

 portionally, than that of this species. In P. effusa the colu- 

 mella is prominent and the whorl falls away from it. In this 

 species there is a prominent rounded ridge outside of the colu- 

 mella, and the latter is, so to speak, inside of the aperture of the 

 shell, which is smaller proportionally, much less product-. 1 above, 

 and less patulous than in P. effusa. A comparison of the dentition 

 shows that the outer laterals of P. eff usa -are more denticulated, 

 having from three to five dentations, while in this species there 

 are normally only three denticles in the outer laterals. The 

 inner portions of both ribbons are, of course, similar. I have 

 examined a radula taken by Mr. Binney from an authentic 

 specimen of effusa, and can testify to this. 



The specimens in question are clearly not /'. eflusa, yet in 

 the absence of typical specimens of P.leoma it still remains 

 doubtful whether they belong to the latter species. Messrs. 

 Adams' description answer- pretty well, except that my speci- 

 mens, instead of being thinner, are much more solid than the 



