60 DESCRIPTION OF NEW 



to determine if there be any undulations there. I doubt when per- 

 fect specimens are found, if there will be any observed. 



The above description and observations being made under the disad- 

 vantage of the examination of a single specimen only, it is proper to men- 

 tion that they may not apply to all. It is very probable that some indivi- 

 duals may have no bifurcation of the spines, while others may have all the 

 spines possessing that character. The colour of the nacre may also vary. 

 Professor Shepard informs me that two other specimens, now in the 

 cabinet of Professor Ravenel, were quite imperfect. "One of them 

 had but two (nearly obliterated) pairs of spines, and the other but a 

 single pair. The shells being eroded in the vicinity of the spines, all 

 traces of them had disappeared. The largest specimen was one-third 

 larger than that now sent." 



The existence of this curious species was first communicated to 

 me by Major Leconte, in 1830 or 1831, and he then very kindly pro- 

 mised to procure it for me through his brother. In a letter recently 

 received from him, he says, "I first heard of, and in fact saw, a frag- 

 ment of the Unio spinosus in the year 1830, as being found, along with 

 several other species (of which single valves were given to me), in 

 the Altamaha River. Since then my brother (Lewis Leconte) has 

 repeatedl}^ endeavoured to obtain specimens of it, without success, until 

 last winter. He once went to the situation where they are most plen- 

 tifully found (a distance of fifty miles, and in an almost uninhabited 

 country), but failed in procuring any."* About two years after Ma- 

 jor Leconte first called my attention to this shell, I found that it had 

 been observed by Bartram in his " Travels." In the summer of 1777 

 he seems to have observed it in the Mississippi. If it be not the same 

 species, it must be very like it. He says, '• The next morning I set off 

 for Point Coupe ; passed under the high pointed cliffs, and then set 

 our course across the Mississippi, which is here near two miles over; 

 touched at a large island near the middle of the river, being led there, 



* Since the above was written, I have a letter from Major Leconte, of New York, (June 

 13, 1836), in which he mentions having just received his specimens of this curious Unio, 

 with some others which are very interesting, and he has kindly promised to place a specimen 

 in rav cabinet. 



