270 , SIX NEW SPECIES 



and anterior basal margins rounded ; anterior dorsal margin 

 slightly rounded — epidermis yellow, but filled completely 

 over with numerous dark green spotted lines, running in a 

 sweep from the beak to the margin. In the anterior part 

 the crowding of these lines generally forms five or six bands, 

 the largest being in the furrow in the middle of the shell : in 

 the posterior part there are no bands — disks transversely and 

 deeply wrinkled, with a slight longitudinal furrow from the 

 beaks to the basal margin — tubercles slightly elevated and nu- 

 merous, and generally situated on the wrinkles ; cardinal 

 tooth wide, depressed and sulcated ; lamellar tooth slightly 

 curved, thick, rather depressed, short and abrupt — posterior 

 cicatrices very distinct, the smaller one being placed directly 

 over the larger one and beneath the point of the lamellar 

 tooth — anterior cicatrices distinct, the great one deep — cavity 

 angular and exceedingly small for the size of the shell — na- 

 cre pearly white and silvery. 



Remarks. — The very minute and delicate spotted lines 

 which pass from the beaks to the margin of this species well 

 characterize it. They are so fine and approach so nearly to 

 each other as to give a general olive appearance to the disk, 

 the ground of which is really yellow. I have not observed 

 this to pervade completely the surface of any other spe- 

 cies, and in this it is constant. The substance of the shell is 

 exceedingly massive and ponderous, more so for its size than 

 any other species which I have seen. The animal is the only 

 one in the organization of which, during my examination 

 of this genus, I have been able to detect any essential differ- 

 ence. From the shell being longitudinal and peculiarly mas- 

 sive, we might be led to suspect a conformation different from 

 the other species, and such is the case. 



By the exertion of my brother T. G. Lea, I have been for- 

 tunate enough to obtain three individuals of this species in a 

 state of impregnation considerably developed. In those I ob- 

 served an appendage, in form of a depressed cone, attached to 

 the branchiae on either side, and a very slight examination 

 fully satisfied me these were the oviducts. 



