512 APPENDIX. 



larger than one of the palpi. Each branchia unites with its 

 fellow at the posterior dorsal extremity, and also in the 

 middle of the dorsal line; it effects, on each side, a very 

 slight junction with each pair of palpi. If that part of the 

 branchial plate which is reflected back and fixed, were free, it 

 would range and lap on its fellow portion, and thus constitute 

 the normal pair of branchiae. If this view is correct, we 

 ought to consider the single plate as essentially a double one, 

 though its component parts are abnormally arranged. The 

 mantle is open on the ventral surface, with the margin irre- 

 gularly scolloped. The liver is dark green. The ovarium at 

 this season is studded with young, and occupies the entire 

 surface of the body between the liver and the foot. 



At one time, from the character of the hinge, we were of 

 opinion that Scrobicularia might have been associated with 

 Syndosmya, but finding the branchiae and palpi of the two so 

 very discordant, we abandoned that idea ; we now think that 

 the genus is superfluous, and that its single species may be 

 transferred with great advantage to the same section of the 

 Tellinae as T. sohdula and T. tennis, with which it agrees as 

 to the soft parts almost precisely ; whilst in the hard parts it 

 only differs in having a semi-internal cartilage, which with us 

 is a point of little or no importance. 



PANDORA OBTUSA. (P. 150.) 



Exmouth, July 1854. 



In our original account of this species, published in Forbes 

 and Hanley's Brit. Moll. vol. i. p. 211, we stated, that there 

 were two palpi, one branchial lamina, and an obsolete one 

 on each side the body; from subsequent observations we 

 were induced to modify our opinion, thinking that there were 

 two perfect branchial plates on each side. A further exami- 

 nation of the animal has proved, however, that our original 

 impression was substantially correct, as the following descrip- 

 tion will show. 



The animal has two very short, reddish-brown, subtriangular 

 palpi, blunt or rounded at their termination, which often 



