60 DESCRIPTION OF NEW 



Accessory Column in the Family Colimacea. 



Wlicn recently cxntniniiig very closely the structure of some of our Ildiccs, I observed 

 what had before escaped my attention, a pillar or an additional colunui, placed like a 

 fulcrum (buttress) in the interior, against the wall of the ordinary column, at the distance 

 of a fifth to a third of a revolution of the whorl from the aperture. I first observed it on 

 the Carocolla sphiosa, (Nobis,) and followed up this discovery until I detected it in a num- 

 ber of species and three different genera, admitting Carocol/a, of Lamarck, and Polygyra, 

 of Say, to be distinct genera, which I think it better at present to recognise. 



This fulcrum, as I propose to call it, in distinction from the central column, varies 

 in form, in size and in place in different species; and at a future period I may give a more 

 exact account and a fuller description than I am enabled at present to take the time to do. 

 It is generally visible from the exterior by the naked eye, when the specimen is thin and 

 in a perfect state. With the assistance of a lens it may be easily seen, though not per- 

 fectly examined and defined. For this purpose it is necessary to fracture the portion of 

 the shell in the vicinity of the fnkrum. It will be found in some species to be a simple 

 round column soldered to the paries of the main column; in others, a compressed or flat- 

 tened column, extending into the cavity of the whorl. 



The purpose of this fulcrum or buttress is very evidently instituted for the greater 

 strength of the ultimate whorl, which being very much enlarged, seems, in some of these 

 more delicate species to require additional support. 



I have detected the fulcrum in the following species, and as several of the species of 

 Dr. Binney and Dr. Gould are unknown to me, I think it likely to be found in some of 

 tlicm. 



Carocolla spinosa. Lea. Helix Icporina, Gould. 



" Edgariana, Lea. " Lecontii, Lea. 



Helix hirsuta. Say. Polygyra Troostiana, Lea. 



" monodon. Racket. " Dorfuilliana, Lea. 



" Leai, Ward. 



It is due to my friend Dr. Leidy to say, that, when I informed him, some months since, 

 of my having observed this fulcrum in many of the Helices, that he at once informed 

 ine that while engaged on the anatomical portion of Dr. Binney's work, which he accom- 

 plished for that zoologist, he had observed in the Helix hirsuta this character of the shell, 

 and advised Dr. Binney of it at the time. But it seems that he did not take advantage 

 of Dr. Lcidy's information, or he may not have himself detected, on examination, this 

 important additional character to these species. 



While I have the Polygyra Troostiana and P. Dorfeuilliana before me, I will take the 

 opportunity to express my dissent to these species being placed by Dr. Binney and Dr. 

 (iou'd, as synonymous with Helix faligia(a,Siiy. They are not only entirely distinct 

 from fatigioti, but are distinct in themselves, and I am sure that zoologists who may 



