213 



species varies from five to seven, but without reference to sex. 

 The very close agreement both in the lingual teeth and in the 

 general internal anatomy of Fusus and Buccinum was men- 

 tioned, and a doubt was expressed as|to the propriety of their 

 wide separation in our present systems of classification. The 

 association of Fusus with Murex, and of Purpura with 

 Buccinum, was also commented upon, and shown by the 

 evidence of the tongues, as well as the general anatomy of 

 the animals, to be clearly incorrect. 



In conclusion, some remarks were made on the method 

 used by the Author, of extracting the tongues from the 

 difi'erent kinds of mollusca, illustrated by specimens, some 

 of which were many times longer than the bodies of the 

 animals, being coiled up near the neck, and brought forward 

 as the teeth are worn away. The Paper was illustrated by 

 beautifully executed drawings of the difi'erent types^ and a 

 series of dissected animals. 



Professor Williamson asked the Author if he proposed to 

 include the Chitons in the order Cyclobranchiata. 



Dr. Alcock was satisfied the Chitons ought not to be so 

 placed; but, judging from the general character of their 

 teeth, he thought they might possibly remain with the 

 Scutibranchiata, or perhaps it would be necessary to establish 

 a new order expressly for them. 



Professor Williamson was glad to learn that this was the 

 result of Dr. Alcock's observations ; for the animals certainly 

 appeared very distinct, and the Chitons, which he remarked 

 have the form of a gigantic woodlouse, were evidently not 

 Cyclobranchiata, as they have a separate gill down each side 

 of the body. 



On adjourning to the microscopes. Dr. Alcock exhibited 

 mounted specimens of tongues from thirty different species of 

 Gasteropoda, with the shells from which they were extracted. 

 One of the lingual ribands was two and a half inches long. 



