48 DESCRIPTION OF NEW 



Cabinet of Mr Buchanan. 

 Diam. 1-1, Length l-S, Breadth 3 inches. 



Shell transverse, inflated, subcylindrical, inequilateral, emarginate at 

 the basal margin, flattened on the sides ; umbonial slope elevated and 

 rounded ; substance of the shell thin ; beaks somewhat prominent and 

 minutely undulated at the tip ; ligament rather short and thin ; epider- 

 mis greenish, darker on the posterior slope; anterior cicatrices conflu- 

 ent ; posterior cicatrices confluent ; dorsal cicatrices indistinct ; cavity 

 of the shell deep; cavity of the beaks shallow; nacre white, bluish on 

 the posterior part. 



Remarks. — I owe to the kindness of R. Buchanan, Esq., a single 

 specimen of this shell. It approaches the A. Ferussaciana more nearly 

 than any other of our Jlnodontx with which I am acquainted. In this 

 individual the beaks are of a bright rusty colour. 



Continuation of Mr Lea's Paper. Read, July 1 5th, 1837. 



Having for some years given much attention to the anatomical struc- 

 ture of the Naiades, I have arrived at some results which may be deem- 

 ed important enough to attract the further attention of zoologists, and 

 be of sufficient interest to merit a place in our Transactions. 



It is a source of congratulation to those interested in the study of this 

 branch of natural history, to find that a number of naturalists are giving 

 their time to examinations in localities peculiarly and fortunately situa- 

 ted in regard to the number of species, as well as their size, which cir- 

 cumstances tend greatly to facilitate investigations. 



Believing that the oviducts would present to us the means of discri- 

 mination in some of the species, having found them to be so very dif- 



