NATURAL SCIENCES OF PHILADELPHIA. 390 



U. r a d i a t u s, Lam. Beautiful specimens occur on the Potomac, with a 

 light green polished epidermis, with broad dark rays, and frequently pencilled 

 rays in the intermediate spaces. 



Margaritana undulata, Say. (Sp.) Very rare. Nacre delicate pink, 

 epidermis in adult shells jet black, much eroded at the beaks. 



M. marginata, Say. (Sp.) I collected a number of specimens. They 

 were all of small size. Epidermis in the young shells elegantly rayed. 



Anodonta f 1 u v i at i 1 i s, Dillwyn.(Sp.) A few individuals were taken ; their 

 surface is almost a uniform duli brown, vastly inferior in beauty to those 

 from the vicinity of Philadelphia. 



A. implicata, Say. One specimen. 



A. e den tula, Say. One perfect young shell, and several larger odd 

 valves were taken ; they exhibit the same uniformity of color as A.Jluviatilis. 



The above shells were all collected within the space of two hours, such was 

 their great abundance. A more prolonged search would doubtless add a few 

 more species to the list, particularly among the smaller terrestrial shells. The 

 Molluscous fauna of Harper's Ferry is distinguished for the development of 

 heavy lines of growth and acute prominent carinas on the shells of the spe- 

 cies ; and in the terrestrial shells, by the depression of the spire. It is strange 

 that a climate which has evidently exercised some influence on the growth of 

 the Mollusca, has still permitted a vast multiplication of individuals. 



On SQUALUS AMEEICANUS, Mitchell, referring it to the Genus 

 ODONTASPIS, Agassiz. 



BY CHAS. CONRAD ABBOTT. 



In his "Report in part of the Fishes of New York," Dr. S. L. Mitchill makes 

 mention of a species of shark, under the title of Squalus Americanus, with the 

 suggestive note, "Caught almost every summer at the very wharves of New 

 York, ten or more feet long." 



Again, nearly a year afterwards, (Dec. 8th, 1814,) in the Trans, of the Lit. 

 and Phil. Soc. of New York, vol. 1, p. 483, he mentions and partially describes, 

 under the same name, this species, as follows : 



"Squalus Americanus. Long-toothed Shark. With oblong sharp teeth, each 

 of which has a little one on each side, at its base. 



This fish is occasionally taken at the very city of New York. He, when he 

 comes, frequents a certain place near the great market, on account of the dead 

 fish and offal thrown into the water there. When the people see one of these 

 sharks prowling about, they bait a hook with a piece of meat or a fish, and 

 not unfrequently catch him. 



The teeth of this species are found abundantly in the alluvial country of 

 North America. They are particularly met with in digging wells near the 

 Potomac and James Rivers. On the former, they are found as high as Alex- 

 andria ; and on the latter, in the city of Richmond itself. The long, sharp, 

 narrow tooth, almost resembling a horse-shoe nail, witli its two little auxili- 

 aries, is very plain and characteristic. This I know, by comparing the fossil 

 Virginian species in my possession with those in the jaws of sharks taken at 

 New York. 



The mouth of one that was killed during the summer of 1813, was nearer 

 the snout than' in many other species. Both jaws had five rows of teeth in 

 front. They were nearly an inch long and not jagged at the sides. Some of 

 them have the rudiments of little teeth on each side, at the base." 



For a third time, in the American Monthly Magazine, vol. 2, p. 328, Dr. 

 Mitchill somewhat describes it, proposing for the species the speoific appella- 



1861.] 



