NEW FRESH WATER AND LAND SHELLS. 219 



spread out on the valve; epidermis very dark brown; cardinal teeth small, 

 crenulate; lateral teeth very long and straight; anterior cicatrices distinct; 

 posterior cicatrices confluent; dorsal cicatrices placed in a row in the cavity of 

 the beaks; cavity of the shell very shallow; cavity of the beaks exceedingly 

 small ; nacre white and beautifully iridescent. 



Remarks. — Since I described the U. cucumoides, from New South Wales, I 

 have received the above described species from Dr. Von den Busch, and by his 

 kindness I am permitted to place it in my Cabinet. It is certainly among the 

 most curious and interesting species which have been observed. The duplex 

 form of the wing is very remarkable. The early growth rises almost perpen- 

 dicularly above the beaks to a point, the succeeding growth forming its sym- 

 phynote fold in a horizontal line, sets off much below the apex of the first 

 growth. The whole presents the appearance of a part being broken out. This, 

 however, is by no means the case. It is a character, and we may observe it in 

 a less degree, but still in a perfect manner in the very young of the U. Icevissimus, 

 (nobis,) which usually if not always at the second growth on the wing, takes 

 a new starting point to form the fold over the ligament. The cardinal teeth 

 are very remarkable, presenting but a small cleft, while the crenulations fill up 

 the space connected with the lateral tooth, in this resembling the Iridina. 

 The margin anterior to the beaks presents the appearance of there having been 

 a wing. Immediately before the cardinal tooth there is a remarkable angular 

 notch in the nacre filled up with laminated epidermal matter. The anterior 

 cicatrices have the peculiarity mentioned in the U. cucumoides, but the three 

 cicatrices are here perfectly distinct. The epidermis is minutely striate over 

 most of the disk; but over the middle part, and on the wing, there may be 

 observed with a lens numerous very remarkable, minute, round granulations. 



Dr. Von den Busch informs me, that he obtained this shell from his friend 

 Mr. Gruner, who, from " its similarity with a dolphin," proposed the name of 

 delphinus, which I have adopted. As the vessel which brought this shell also 

 visited some of the islands of the Indian Ocean, Mr. Gruner thinks there may 

 be some doubt of its inhabiting New Holland.* 



* Since this paper went to press, a letter received from Dr. Von den Busch, informs me that this shell 

 came from the "river Souzi, on the coast of Malacca." 



vin. — 3 F 



