120 Mr. J. Hogg on some Amphibians. 



It has a remarkable analogy to the singular vesicular develop- 

 ment of the cement-tissue of the peduncle of Lepas (Dosima) 

 fascicularis, Sol. & Ellis*. 



The byssus in the Acephala is generally corneous ; but in 

 Anomia it forms a calcareous plate (the plug), possibly corre- 

 sponding with the opercular valve in Hipponyso and Lithedaphus, 

 which may be considered a calcareous secretion of the ventral 

 face of the foot. The epiphragm of the Helices would also 

 be homologous, if this plate be really a secretion of the foot, 

 as M. P. Fischer states; but it is probably secreted by the 

 mantle, like the septa of Vermeti, Runcina decollata, &c. To this 

 category belong probably the tubes of Teredo, Gastrochcena, 

 Clavagella, &c, and the accessorial valves of Pholades. The two 

 pallets in Teredo, which have a striking analogy to the opercula 

 of some Serpula (Hijdroidcs norvegica, Gunn.), might perhaps be 

 compared with the posterior supplementary shells of Talona. 



The shell of Argonauta, considered by Mr. Adams to be homo- 

 logous with the egg-cases of Murex, agrees with Nautilus in its 

 position and the black colour of the carina; but it seems to be 

 formed by the arms only. Its homology is therefore uncertain. 

 It appears that all parts of the skin in Mollusca can secrete a 

 shell. There are likewise found calcareous spicula or grains in 

 all parts of the body, in the clypeus in Gymnobranchia, the 

 tentacula of Pleitrobranchus, and even in the intestinal channel. 

 Iu the Bullida and some Pellibranchiata there are thick calca- 

 reous plates in the stomach. 



Note. The ligament is a thickening of the epidermis, which 

 is part of the skin of the animal, but not specially of the shell. 

 This seems evident to me from examining, for instance, a specimen 

 of Mi/a truncata in spirit. The connexion of the two valves by 

 the ligament proves, therefore, not that the valves were originally 

 one only, but that the bivalve shell is formed in the same manner 

 as the two lateral mandibles of the jEolidce. 



XIV. — Notes on some Amphibians. 

 By John Hogg, M.A., F.R.S., F.L.S. &c. 



Dr. J. E. Gray, in his paper "On the Clawed Toads {Dactyle- 

 thra) of Africa," published in the ' Annals and Magazine of 

 Natural History' (vol. xv. p. 334), well observes, that this 

 kind has " large webbed hinder feet, some of the toes of which 

 are armed with very distinct horny black claws — a peculiarity 

 of structure that is quite an exception amongst the Batrachian 

 animals." 



* Darwin's ' Cirripeds,' p. 96. 



