398 Dr. J. E. Gray on some Families of Bivalve Shells. 



G. killing a couple of deer iit Candavilly ; G. also nearly added me 

 to the list of killed, for having separated from each other, his rifle- 

 ball passed through the neck of a fine buck, and turning against the 

 spine, glanced over my head. 



Leaving the buggy and cart to follow at leisure, G. and I galloped 

 over to Mohomalie, where D., whom you may remember I had left 

 at Karandie, was now stopping. Our friends hardly knew us, soiled 

 and travel-worn as we were, and vdth beards several inches long. A 

 hearty welcome and a recapitulation of our adventures made the 

 evening fly swiftly, and by daylight next morning we took Her Ma- 

 jesty's mail for Jafi^ua, from whence I now "wish you heartily 

 farewell." E. L. Layard. 



XXXVII. — A Revision of the Genera of some of the Families of 

 Conchifera or Bivalve Shells. By J. E. Gray, Ph.D., F.R.S., 

 V.P.Z.S. &c. 



[Continued from p. 44.] 



Some conchologists have been inclined to pay great attention to 

 certain characters in the animal and marks on the Bivalve shell, 

 which the examination of an extensive series show^s to be of only 

 secondary importance in some genera and species. 



1. The existence and depth of the siphonal sinus in the 

 submarginal scar have been considered of the greatest import- 

 ance, for it is believed that its depth shows the length, and its 

 absence the absence of the siphons. 



When the inflection is very deep, it does show that the animal, 

 as in Tellinidce, has long and retractile siphons, for the inflection 

 is produced by the edge of the fan-like muscle which retracts the 

 siphons; but several genera of Corbiculidce and Lucinidce have 

 well-developed siphons though they have no inflection; but 

 then the siphons of these genera are only contractile, and not 

 withdrawn into the cavity of the mantle by any special muscles. 



In some genera with retractile siphons, the length of the siphons 

 and consequently the depth of the siphonal inflections vary con- 

 siderably in very nearly allied species, sometimes so much so, 

 that the presence of the siphons in several species is scarcely to be 

 discovered. This is the case with certain species of Chione, and 

 they thus gradually pass into the genus Circe, which have all the 

 other characters of that genus. Yet Messrs. Forbes and Hanley 

 (Brit. Moll. i. 446), on this character, place Chione in Venerida, 

 and Circe in the family Cyprinadce with Astarte and Isocardia. 



It may be observed, that there are other families as well as Vene- 

 rida-, which generally have elongate retractile siphons and deep 

 siphonal inflections, that contain some species which are without 



