1856.] 163 



with spiculae. Some of the second variety of tubes are constituted of a confiu- 

 ent pair, the throat of which bifurcates at bottom. Both kinds of the tubes are 

 very slightly contractile, and under irritation may gradually assume the appear- 

 ance of superficial wart-like eminences within the perforations of the shell occu- 

 pied by the sponge. Water obtains access to the interior of the latter through 

 the more numerous tubes, and is expelled in quite active currents from the 

 wider tubes. 



In structure the sponge is composed of an intertexture of granular matter and 

 pin-like silicious spicula^. Several species of Cliona are indicated by European 

 naturalists, but are not characterised with sufficient detail to determine 

 whether the one above indicated is distinct or not from them. 



Dr. L. further added, it might appear only of scientific interest to observe a 

 structure so low as the sponge is classified in the organic kingdom, endowed 

 with the power of penetrating such dense and hard bodies as the shell of the 

 clam and oyster, but he suspected that the agency of the boring sponge was a 

 highly important one in the sequence of natural phenomena, as it is a means by 

 which dead shells are rapidly decomposed to be dissolved in the ocean water, 

 where they may again serve as the elements of construction of the habitations 

 of the rising generations of molluscous animals. In confirmation of this view 

 Dr. L. stated, that an extensive bed of oysters, which had been planted by Mr. 

 Thomas Beasley, at Great Egg Harbor, and which was in excellent condition 

 three years since, had been subsequently destroyed by an accumulation of mud. 

 The shells of the dead oysters, which were of large size and in great number, 

 in the course of two years have been so completely riddled by the boring Cliona 

 that they may be crushed with the utmost ease, whereas without the agency of 

 this sponge the dead shells might have remained in their soft, muddy bed, 

 devoid of sand and pebbles, undecomposed perhaps even for a century. 



September 23d. 



Mr. Ord, President in the Chair. 



Mr. Lea presented a paper entitled, " Description of the Bjssus in 

 the genus Unio, by Isaac Lea," which was referred to a committee con- 

 sisting of Dr. T. B. Wilson, Dr. Bridges, and Mr. Vaux. 



September SOth. 



Dr. Bridges, Vice President, in the Chair. 



The Committee on Dr. Leidy's paper read [^2d inst., on Dr. Girard's 

 paper read 9th inst., and on Mr. Lea's paper read 23d inst., severally 

 reported in favor of publication in the Proceedings of the Academy. 



Notice of some remains of extinct Vertebrated Animals. 



By Joseph Lkidy, M. D. 



1. Leptauchenia major, Leidy. In an examination of a collection of fossils 

 obtained by Dr. F. V. Hayden, in Nebraska, for the St. Louis Academy of Science, 

 I observed the mutilated jaws of a larger species of Leptauchenia than that pre- 

 viously characterized under the name of L. decora, (Pr. A. N. S., Phila., viii. 88.) 

 In the upper jaw there are seven molars, forming nearly a continuous row, pre- 



