300 [Decembee, 



December \Qth. 

 Mr. Lea, Vice President, in the Chair. 



Letters were read 



From Prof. J. P. Kirtland, dated Cleveland, Ohio, Nov. 24th, 1856, 

 transmitting a specimen of Bohemian Waxwing, (Bomhy cilia gar rula,) 

 from that neighborhood. 



From the Dublin University Zoological and Botanical Association, 

 dated Trinty College, Dublin, Nov. 28th, stating that their printed Trans- 

 actions had been transmitted to the Academy, and desiring exchanges. 

 Referred to the Publication Committee. 



The following papers were presented for publication in the Proceed- 

 ings : 



" Classification of the Vegetable Kingdom. By T. G. Hilgard, M. D ;" 

 referred to a Committee consisting of Mr. Durand, Dr. Uhler and Dr. 

 Rand. 



" Notice of remains of extinct Turtles from New Jersey, &c. By 

 Joseph Leidy, M. D. /' referred to a Committee consisting of Dr. Le 

 Conte, Mr. A. H. Smith and Mr. Ashmead. 



Mr. Cassin read a letter from Mr. P. B. Du Chaillu, dated Corrisco, 

 Gaboon, Oct. 15th, 1856, transmitting a large and valuable collection of 

 objects in Natural History, and giving an interesting account of his ex- 

 plorations. On motion of Dr. Le Conte, Mr. Cassin was requested to 

 prepare an abstract of the letter for publication in the Proceedings. 



Mr. Lea mentioned that, in describing a new species of Triquetra, Klein. {Hyria. 

 Lam.) in April last, (Proceedings, vol. viii. p. 79,) he had but a single valve, 

 which had the appearance (as stated in his remarks not yet published) of being 

 twisted like Area tortuosa, Lin. This extraordinary form, which bad never been 

 suspected to exist in any member of the family Naiades, excited great interest 

 with the zoologists who saw it; but it was still a matter of doubt whether the 

 curve, although exceedingly regular and presenting no appearance of constraint 

 or injury, might not be abnormal. This doubt has now, however, been put entirely 

 at rest, for the curve of both specimens is so precisely the same, that when the 

 odd right valve is placed against the left of the other, they fit perfectly, proving 

 that the curve is a mathematical law belonging to the species. He exhibited to 

 the Society a complete adult specimen, which H. Cuming, Esq., of London, sent 

 him for inspeetion and to be figured. The species was recognized by Mr. Cum- 

 ing on his visit here recently at once to be the same as that in his cabinet, and 

 he promptly and liberally offered to place this unique specimen in Mr. Lea's 

 hands for a more perfect description and figure than could be given of the single 

 immature valve he already had. Mr. Cuming's specimen is quite six inches along 

 the dorsal line to the angle of the posterior margin, and this line deflects quite 

 two inches in the course of the six inches from a straight line, and it is so 

 twisted that the basal margin at the posterior end turns up to be on a plane with 

 the dorsal line at the beaks. This remarkable curve causes the long lateral 

 teeth to have a curve of double curvature. The greatest distance from the dor- 

 sal to the basal margin is one inch and three-tenths. The greatest diameter is 

 nine-teuths of an inch, which gives it a sub-cylindrical form, and it is not unlike 

 a twisted banana, (3Iusa sapientum). This perfect specimen presents the superior 

 portion of the valves covered with small, regular tubercles, which was not sus- 

 pected in the original single valve, there being on it only a few irregular undu- 

 late markings. Mr. Cuming's specimen settles the doubt as to habitat. He re- 

 ceived his from Shanghai, and therefore Mr. Fitch and Dr. Tngalls, to whom I 



