214 [September, 



Byssanodonta Paranensis, (V03'. dans I'Ameriqiie Merid.) This always remains 

 attached by a byssus, proceeding from the foot. It has amterior and posterior 

 adductor muscles. 



In the examination of the soft parts of a very large number of species of this 

 family, from Georgia, which I have been enabled to do through the kindness of 

 Bishop Elliott, I have noticed in the adults of two small species, a perfect bi/ssus 

 attached to the lower portion of the foot, posterior to the base. 



In dissecting five specimens of Unio acuiissimus, nobis, from Etowah River, 

 Georgia, I found in a full grown specimen, one and a quarter inches wide, a 

 large fine byssits, fully an inch in length, thicker than a horse hair, quite flattened, 

 semitransparent, and without any appearance of fibre, but rather hornlike. At 

 the point of insertion in the foot, the filament is a little enlarged and rounded, 

 and there is also at the same point the rudiment or remains of a second one. 

 The other extreme end of this filament, where it was attached to the foreign sub- 

 stance to which the animal had anchored itself, is evidently perfect, shewing the 

 true length of the bi/ssus. At this end it is divided into four branches, undoubt- 

 edly having been attached. Of the five specimens before me, one only has the 

 byssus remaining ; but it is evident, from the fact that each of the others has a 

 longitudinal cicatrix at the point of the former attachment, that every one had 

 been furnished with a byssiis. 



I found also that the same kind of byssus existed in the adult of the closely 

 allied species, Unio Conradicus, nobis, which accompanied the above from the 

 same locality. There are three of this species, one of which has a portion of the 

 byssus attached in the same manner, but evidently broken off and not being more 

 than the fourth of an inch long. This filament is much more delicate than that 

 described above, not being thicker than a human hair. It is not flattened, but 

 rounded. Close to its insertion in the foot is a second one, shorter and probably 

 the remains of a separate filament of attachment, the genus Pinna having in- 

 numberable fine threads of attachment, the shell itself of one species being some- 

 times found more than two feet in length. 



In all the eight specimens of the two Unioncs above mentioned, the impressed 

 cut or cicatrix made by the byssus is very observable, so that there cannot re- 

 main a doubt, but that they had all been attached until they had arrived at 

 adolescence. 



As part of these were no doubt anchored when taken from the water, and 

 part of them free and locomotive, it appears that it cannot be necessary to 

 their existence that they should retain their normal condition of attachment. 



There are other allied species, forming with these a group, oi Vihich acutissimus 

 is the type, which I have not had the advantage of examining ; but I have no 

 doubt that those will all be found to be also anchored by a byssus, in the same 

 manner. 



These facts will I hope draw the attention of the Zoologist more closely to ob- 

 serve the habits of this family. 



Dr. LeConte, on behalf of the Committee appointed to revise the 

 "list of members and correspondents of the Academy, presented a cor- 

 rected copy of the list ; which report was adopted, and the Committee 

 discharged. 



The Corresponding Secretary read his report for September. 



EliECTION. 



Mr. Wm. Gr. Binney, of Germantown, Dr. Wm. Smith Forbes, and 

 Mr. Wm. Weightnian, of Philadelphia, were elected members of the 

 Academy. 



