204 



Prof. J. Wood-Mason and Mr. A. Alcock. [Nov. 26, 



2. On the Parturient Female and New-lorn Young of Trygon. 



walga. 



Two females of Trygon walga, Miiller and Henle, were taken at 

 Cocanada, in the Godavari Delta, on the 8th. of April of this year. 

 The abdomen, in one of them, was so much distended that the 

 normal flat shape of the fish was obscured. On transfer of this 

 specimen to a bucket of sea-water, two young ones were seen to be 

 suddenly extruded from the cloacal orifice one a few minutes after 

 the other. The young ones swam about vigorously in the bucket. 

 Kelatively to the size of the abdominal cavity of the mother, which in 

 this species is much contracted, the young ones are enormous; and 

 on seeing the two of them beside the open maternal abdomen it 

 appears almost incredible that they could ever have been compressed 

 into such a confined space. 



The following are the measurements of the mother and offspring, 

 with their weight after preservation in spirit : 



Both young ones were females ; neither of them had any traces of 

 external gill filaments ; both of them had a small papilliform um- 

 bilical vesicle about 1 mm. long. The spiracles in both were large 

 and widely open. 



Before going on to describe the visceral anatomy of th young, and 

 the structure of the uterus and its trophonemata in the adult, there 

 are certain interesting external characters, distinguishing the young 

 from the mature female, which are important enough to be men- 

 tioned. 



(1.) In the young, the dorsal surface of the body is quite smooth 

 and devoid of the dermal tubercles which, in this situation, charac- 

 terise the adult. (2.) The young have only one tail spine, whereas 

 the adult has two, and in front of them along series of fixed spinelets. 

 (3.) The middle third of the space between the base of the tail spine 

 and the tip of the tail is occupied in the young one by a median fold 



