94 PROCEEDINGS OF THE ACADEMY OF 



that of Professor Agas«iz, who has examined and compared the one with the 

 other. I would add that my conjectures as to the new species being found 

 at the terminus of the tide in the tributaries of the Delaware river have 

 proved correct ; as I have since ascertained that it is taken in March in the 

 Brandywine below the dam at the head of tide, as well as at, the foot of the 

 rapid water at Trenton, appearing for a short time before spawning and 

 apparently only for that purpose. 



My object in this communication is to establish this as a distinct fish and 

 give it a specific appellation, as well as to settle any question of priority of 

 description which may hereafter arise. 



I have presented this evening a small vial which holds the contents of the 

 stomach of a northern smelt, O. viridiscms, as being suggestive of the vast 

 amount of fish food accessible to marine species in winter as well as in 

 summer. The vial contains three shrimps, one of the small fry of some other 

 fish, and a half dozen fish ova not quite as large as those of our brook trout. 

 The ova have made no profiress in the process of incubation, from which I 

 infer that they were seized by the Osmerus as soon as they were ejected, or 

 not long after they were deposited by the parent fish. In observing the 

 habits of both species above referred to, I have found them to go to the head 

 of tide, but no further, for the purpose of spawning. This occurs as soon as 

 the rivers are free from ice in the spring, when the nortberu smelt is taken 

 in such numbers from the Gulf of St. Lawrence as sometimes to be used as 

 manure. 



Description of Nine Species of UNIONID.S from Lake Nicaragua, Central 



America. 



BY ISAAC LEA. 



In the "Proceedings of the Acad, of Nat. Sci.," April, 1856, I described a 

 new species of Triqueta [Hi/ria Lam.), which I called lanceolata. It was made 

 from a single valve in a collection from China. In the diagnosis made in the 

 Proceedings it was not mentioned that this valve was somewhat twisted, being 

 fearful that the curved condition arose from accidental circumstances, and 

 not from a normal condition like Area torfiosa, Lin. Subsequently, in the 

 " Journal of the Academy," vol. iii, and in " Observations on the Genus Unio," 

 vol. vi, I published a full account of this peculiarly interesting species, having 

 received perfect specimens, one of which was well figured. In this paper I 

 thought that, as the original name of lanceolata, made from a single imperfect 

 valve, did not aj)ply to the perfect shell, science would be subserved by a de- 

 scriptive name. I proposed to call it contorto, and redescribed it under that name 

 with full remarks and observations. At that time it was the only member of the 

 family Unionidx, which was known not to be equivalve. Subsequently, in de- 

 scribing a species of Spafha, under the name of Natalensis, I mentioned that it 

 was "slightly inequivalve." "Journal Acad. Nat. Sci.," vol. vi, aud in "Ob- 

 servations on the Genus Unio," vol. xi. 



In 1865 I published in the " Proceedings of the Academy" the diagnosis of a 

 new Unio from China, which is inequivalve ?iX\^ twisted. This I named tortuoms. 

 The full description and figure, with remarks, is in a paper which I have pre- 

 pared for the Journal of the Academy. These constitute all the inequivalve 

 species of the family which I have seen until recently. 



The collection made by the late Mr. Thomas Bridges, botanist, who, during 

 his travels in Central America, visited Lake Nicaragua, has been kindly placed 

 in my possession, part by Col. E. Jewett, and part by Mr. W. M. Gabb, Paheon- 

 tologist of the California Geological Survey. Very much to my surprise and 

 satisfaction I found that several species of Unio and Anodonta had this 

 inequivalve character. 



It may be here remarked that there seems to be a predisposition, in the 

 Unionidae of Cential America, to this very unusual character in the Unionidne, 



[March , 



