Mr, Lea on the JVaiades. 548 



valves connate, — it appears to us a real improvement, and one for 

 which he deserves the thanks of all conchologists. In the same 

 page it is said, " he (Lea) proposes also, the fusus fluviatilis of 

 Say, as a new genus; for the reason that the canalifera are 

 universally pelagian shells, while this is a fluviatile species, and 

 therefore falls within the melaniana. He calls it the lo fusi- 

 roRMis." Let us examine what this real improvement is. The 

 family of the naiades consists of fluviatile shells. Lea divides 

 it into two genera, unio and symphynota. The distinctive cha- 

 racter of the first is valves free, of the last valves connate, or not 

 free; the testaceous covering of the shell being extended over 

 the ligament, and uniting the valves, so that they cannot be 

 separated without a fracture of the testaceous covering. Lea 

 then substitutes for Say's fusus fuviatilis, a new generic term, io, 

 and converts Say's generic term into a specific one, changing 

 the fusus Jluviatilis of an old discoverer into io fusiformis, " sa- 

 tisfied that 720 gejius should contain pelagian and fluviatile shells 

 in common." [Vide page 138, paper read before A. P. S. 1831.] 



In the meantime, Mr. Lea and his eulogist, wrapped up in 

 their real improvement, could not see that all this machinery was 

 held together with a rope of sand, and that at the least touch 

 the genus Symphynota must all fall to pieces, since several pela- 

 gian genera, such as Pinna, Mytilus, Modiola, Hyalea,* &c. &c. 

 are connate, as well as the unios, upon which the genus Sym- 

 phynota is founded. This is double suicide on the part of Mr. Lea, 

 both of his real improvement, and of his claims to nice discrim,i- 

 nation ; he revolutionizes Mr. Say's labours, upon the express 

 ground that " no genera should contain both pelagian and fluvi- 

 atile shells," whilst he himself creates a genus Symphynota for 

 connate shells, which are both marine and fluviatile. His eulo- 

 gist calls this real improvement. Those who understand concho- 

 logy, find in Rafinesque's genus Metaptera, all the suflicient cha- 

 racters for the genus Lea would create, and much more distinc- 

 tive than those implied by the term Symphynota, which is proper 

 only to a family. I shall now proceed to specify, in a more de- 

 tailed manner, the causes for striking from Mr. Lea's new species, 

 twenty-five out of twenty-six. 



Unio occidens. — Lea. Tr. A. P. S. vol. 3, plate x. fig. 16, is 



* " The valves of the Hyalea are connate." — Dtinonifurt, 1808. 



