136 Zoological Society. 



creases as the load increases. He also shows, that the rate of tra- 

 velling with a given load does not depend solely on the tractive 

 power of the engine, but that another important element enters into 

 the calculation, viz. the evaporating power of the boiler. An ap- 

 pendix contains a detailed account of expenses, profits, and other 

 valuable particulars of a mercantile and speculative nature, drawn 

 from the documents of the Liverpool and Darlington railways. Alto- 

 gether, the work is written in a clear and unaffected style; the sub- 

 jects throughout are treated very philosophically, and with great 

 ability; the typographical execution is also exceedingly creditable, 

 and, judging from the gratification we have experienced on its per- 

 usaljwe can have no hesitation in pronouncing it an elegant aqd truly 

 valuable publication, that should be possessed by all persons inte- 

 rested in such pursuits. 



XXXII. Proceedings of Learned Societies. 



ZOOLOGICAL SOCIETY. 

 Dec. 22, SPECIMENS were exhibited of numerous Shells of the 

 1836. ^ genus Mitra, Lam., and of one species of Concelix, 

 Swains., forming part of the collection of Mr. Cuming; and an ac- 

 count of them by Mr. Broderip was read, commencing as follows : 



" The species of the genus Mitra, Lam., which I am about to de- 

 scribe had been sent by Mr. Cuming, in whose cabinet they are, to 

 Mr. Swainson, whose intimate acquaintance with this family renders 

 him so particularly competent to the task of describing them. They 

 were named by him, and he also made notes respecting them before 

 returning them. In the following account of them I have retained 

 Mr. Swainson's name in every instance but one : and whenever he 

 has made any WTitten observations I have quoted them. 



Characters, habitats, &c. of the following species were then given, 

 and are printed in the " Proceedings." 



Genus Mitra (/-am. and SjrazMS.). Mitra nebulosa (representing 

 nubila. Type 5, 1, Sw.), Swainsonii (Type 1, 1.), Ancillides (5, (2 ?)), 

 maura (representing Tiara foraminata, Type 1, 4.),/ulvescens (5, 1.), 

 testacea (5, 1. representing /ufca), fulva var. (1, 2. representing 

 Tiara), chrysostoma (5, 1. representing /en-wjrjnea), tristis (2, 4.), and 

 effiisa (1, 5.). 



Genus Tiara, -Swflzws. (Mitra, Lam.) Tiara foraminata {repTe- 

 senting Mitra maura, T}'pe 2, 4.), muricata, mucronata, catenata 

 (1, 3.), multicostata, rosea (1, 2.), millecostata (the close-set longi- 

 tudinal ribs and cancellated base give this shell, which may not have 

 attained its full growth, the aspect of a Cancellaria), lineata (5, 1), 

 nivea (5, 3.), aurantia, terebralis, crenata (5, 3. or 3, 3.), rubra (1, 2.), 

 semiplicata, and attenuata (5, 1). 



Mr. Swainson had written on the paper containing Tiara tere- 

 bralis, " Type 4, 4. This is one of the most extraordinary shells in 

 the collection, as it so closely resembles the Mitra Terebralis that. 



