290 Zoological Society. 



of Europe *, and a fifth has been received from the Himalaya momv 

 tains." The discovery of six distinct species in India, which have 

 mostly been collected in Nepal by B. H. Hodgson, Esq., one from 

 Japan, and the two described by Dr. Brandt, making in all twelve 

 species, is accordingly no small accession to the known species of 

 this interesting genus. 



June 13, 1854. — Dr. Gray, Vice-President, in the Chair. 



On the Genus Mulleria, Sowerby, or 

 AcosT^A, d'Orbigny. 



By Dr. John Edward Gray, F.R.S., P.B.S., V.P.Z.S. 



M. d'Orbigny has very kindly transferred to me the specimens 

 of the shells which he described, in the 'Rev. et Mag. Zool.' 18.51, 

 under the name of Acostcea Guaduasana, and which he had received 

 from Rio Sero near Guad\ial (Rio Magdalena) in Bogota. The ex- 

 amination of the specimens proves the truth of the supposition which 

 I formerly expressed, that Mr. Sowerby' s genus Miilleria was de- 

 scribed from an imperfect specimen of this shell which had lost its 

 umbones, with the young free state of the shell attached to them, 

 in the manner so characteristic of this genus. 



The series of specimens consists of a pair, not in a very perfect con- 

 dition, and without the produced umbo of the attached valve, like 

 the specimen described by Mr. Sowerby, but in a less worn con- 

 dition, four specimens of the attached valve, and several of the free 

 upper one. 



The series of attached valves is curious, as showing the very dif- 

 ferent state of the umbo, the manner in which the free valves 

 are modified before one of the valves becomes fixed ; also the man- 

 ner in which the upper free valves separate from the free part by a 

 natural crack, when the free valves become united together by their 

 edges, forming a shelly tube. In two of the specimens this crack 

 takes place almost immediately behind the posterior end of the sym- 

 metrical free shell ; in two of the others, the hinder part of the 

 free shell is dilated into a triangular irregular portion before the 

 hinder older part of the upper valve separates from the young one ; 

 in one of these the triangular tube thus formed is narrow and elon- 

 gate ; in the other, broad, forming a nearly equilateral triangular 

 cavity under the umbo of the attached valve. 



In three of the five specimens the shell is attached by the outer 

 surface of the right valve, and in the other two by that of the left 

 valve ; the three specimens attached by the right valve exhibit all 

 the three variations in the form of the umbo, viz. the absence of the 

 free shell, the small, and the large and much dilated state of it. 



There can be no doubt, as far as one can undertake to determine 

 from the examination of the shell alone, of the aflSnity of this genus 



* One of whicli s])ecies is in all probability the so-called Accentor Calliope of 

 Tenini. v. C'alliopr Camtschafkennis, Gmel., whicli, certainly, has no affinity to 

 Accentor. 



