British Association. 129 



exceptional in the structure of its shell, was now shown to be con- 

 nected with the surrounding families by Mya, Thracia, Anatina, and 

 other genera of Myadcc, whose characters were of an intermediate 

 nature. In the class Echinodermata, Dr. Carpenter extended and 

 confirmed the results he had before given respecting the minute 

 structure of their skeletons/which preserve a remarkable conformity 

 throughout the group, extending to the small calcareous plates met 

 with in the Holothuridce. Dr. Carpenter had also ascertained that 

 the same minute structure existed in the Nummulite with the small 

 existing foraminifera described by Ehrenberg ; but that the supposed 

 Nummulites brought by Mr. Pratt from Bayonne presented several 

 forms of structure entirely distinct from that of the true Nummulite. 



'• On the Sounds produced by one of the Notonectidce under 

 Water." By Mr. Ball. 



He stated, that the fact having been mentioned to him some two 

 years since, he had not had an opportunity of testing the observation 

 until within the last few days, when a specimen was brought to him 

 in an ordinary jelly-glass ; it was, he believed, the Corrixa affinis. 

 When suspended in the water, about four inches below the surface, 

 it emitted three short chirrups, and then a long cricket-like sound. 

 It appears the sounds are emitted in the evening and night, and are 

 so loud that they may be heard in an adjoining room, and are con- 

 tinued during the night. Mr. Ball stated that time did not permit 

 him to make any accurate observation ; but he thought the matter 

 so curious, that he noticed it with the view of attracting the atten- 

 tion of entomologists, in the hope of obtaining an explanation of the 

 manner in which this noise is produced under water. 



" On the Scientific Principles on which Classification in the higher 

 Departments of Zoology should be based." By Mr. Ogilby. 



The dental system was, no doubt, a valuable means of diagnosis, 

 and this depended upon the fact that it had a relation to the stomach 

 and other viscera intended for the digestion of food. Just in the 

 same way, the extremities of the mammalia, more particularly the 

 fore-arm, are the exponents of the habits, mental power and oeconomy 

 of animals. The fore-arm is the seat of the function of locomotion, 

 of manipulation and touch. According to the real position of an 

 animal in the scale of organization will be the character of its fore- 

 arm. This position was illustrated by examples from the various 

 families of mammalia. He thought, that in our usual systems of 

 zoology a too exclusive regard had been given to the structure and 

 form of the teeth. 



Mr. W. Thompson read a letter from Mr. Alder, dated Salcombe, 

 June 17, 1845, in which the writer stated that he had lately obtained 

 in Torbay at least ten, and perhaps twelve new species of Mollusca 

 nudibranchiata, to add to the British fauna. They consist of four 

 species of Doris, five or six of Eolis, and an animal of an entirely 

 new genus, approaching nearest to Tritonia. A singular species of 

 moUusk obtained at the same time, resembling in general appearance 

 the genus Pelta of Quatrefages, was noticed in detail. 



