Zoological Society. 379 



Owen, vol. iii. pi. 49, the tarsus is seen to consist of a single bone, 

 terminating in three distinct knuckles, for the articulation with the 

 metatarsal phalanges ; while the thumb is seen with its different 

 joints on the posterior and inner aspect, and in its natural position. 

 This part of the leg has long been mistaken by ornithologists : Prof. 

 Owen calls it tarso- metatarsal, and Dr. Melville views it as the meta- 

 tarsal, which Dr. Macdonald asserts is surely more erroneous than 

 even Prof. Owen's view. 



" The thumb or great toe very often disappears in the endoskeleton, 

 but may sometimes be seen in the exoskeleton, as in the leg of the 

 Horse and some other mammals, where the metatarsus is fused into 

 a single or shank- bone, terminating in a single phalanx as in the 

 Horse, or double phalanx as in the Llama. 



" Dr. Macdonald also briefly alluded to the nomenclature adopted 

 by entomologists and other annulose zoologists, and maintained, that 

 if the nomenclature of the anatomist was to be appropriated by them, 

 they were bound to use the terms anatomically ; and then submitted 

 the following sketch of the homologies of the posterior leg : — 



Coxa = Cotylon. 



Trochanter = Femur. 



Femur = Tibia. 



Tibia = Tarsus and great toe. 



Tarsus = Metatarsus and phalanges. 

 " These homologies are easily traceable in all the six legs of the 

 Entomoid classes, and also in the thoracic legs of the Crustacea, and 

 are particularly well-marked in the large claw of the Crab, where the 

 lines and markings point out the metatarsal and digital phalanges, 

 terminating in the large claw ; where the thumb or opposable claw is 

 jointed to what may be viewed as homologous to the tarsus, while 

 the rest is the fused terminal phalanges." 



The communication was also accompanied with a verbal explana- 

 tion of the several diagrams exhibited. 



December 12.— R. C. Griffith, Esq., F.G.S., in the Chair. 

 The following papers were read to the Meeting : — 



1. On the Habits of a living specimen of Nanina vitrinoides 

 (Desh.). By H. E. Strickland, F.G.S. 



On the 2nd of December, 1847, Capt. W. J. E. Boys presented me 

 with three specimens of a terrestrial mollusk, named Nanina vitri- 

 noides, by Mr. Gray (P. Z. S. pt. 2. p. 58 ; Helix vitrinoides, Desh.). 

 Capt. Boys had procured them a considerable time before, certainly 

 not less than a year, in the district of Ajmeer in Upper India. The 

 animals still remained within the shells, but from the length of time 

 during which they had been kept dry they were greatly reduced in 

 bulk, and had almost wholly retired from the outer volution, as was 

 easily seen from the transparency of the shell. Like many of the 

 Helicidce of hot climates, especially those which are exposed to long 

 intervals of drought, the Nanina vitrinoides secretes a calcareous poma, 

 or deciduous operculum, every time that it retires into a state of 



