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 Myade, 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 Holothuride. 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 Notonectide 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 Corrira. affnis. 
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. Bali 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 ceconomy 
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 Holis, and an animal of an entirely 
new genus, approaching nearest to Tritonia.. A singular species of 
mollusk obtained at the same time, resembling in general appearance 
the genus Pelta of Quatrefages, was noticed in detail, 
