854 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [136] 



Habitat — Trygon centrum, stomach and pylorus. August, 1884 and 

 1887. Wood's Holl, Massachusetts. 



Upon four different occasious I have obtained a few Tetrarhynchi from 

 the stomach of the sting ray (Trygon centrura), which, with the some- 

 what hurried examination that was made of them while they were alive, 

 were supposed to belong to the same species. After an examination of 

 the alcoholic specimens, however, I find that there are two entirely dis- 

 tinct species in each of the four lots. These differ from each other most 

 in the character of the booklets on the proboscides, T. tenue, having 

 minute spinose booklets, while the booklets of T. robustum are short, 

 stout, and strongly recurved. 



Tbese parasites were found as follows : 



Date of capture. 



No. of ray8 

 examined. 



August, 1884... 

 August 1, 1887. 

 August 8, 1887. 

 August 10, 1887 



No. of para- 

 sites found. 



One. 

 Two. 

 Three. 

 One. 



These specimens were all found either in the stomach proper or in 

 the pylorus. 



Of the following measurements No. 1 was a living specimen, the 

 others alcoholic : 



Dimensions. 



Length , 



Length of bothria , 



Breadth of head. 



Length of head and neck 



Diameter of neck. , 



Length of contractile bulbs 



Breadth of contractile bulbs 



Length of proboscides 



Diameter of proboscides 



Length of hooklets 



Breadth of hooklets 



Length of anterior segment, approximate 



Breadth of anterior segments 



Length of posterior segments 



Breadth of posterior segments , 



No. 1. 



mm. 



19 00 

 0.46 

 0.30 



0.24 

 0.14 

 0.05 



0.04 

 0.18 

 1.16 



0.70 



No. 2. 



mm. 



20.00 

 0.36 

 0.24 

 0.56 

 0.18 

 0.11 

 0.05 

 0.28 

 0.02 



0.02 

 0.12 

 0.88 

 0.58 



No. 3. 



mm. 

 13.50 

 0.40 

 0.26 

 0.48 

 0*20 

 0.12 

 0.04 

 0.20 

 0.026 

 0. 0055 

 0. 0014 

 0.02 

 0.16 

 0.80 

 0.24 



In No. 1 the diameter of neck at collar was 0.18 mm ; length of neck 

 proper, 0.40 mm ; length of collar, 0.14 m,n ; length of bothria, varying from 

 0.3G to 0.56 ram ; posterior segments, from 0.94 to 1.16 mm . • 



In an alcoholic specimen, 13 mm in length, the length of the head and 

 neck was 0.78 mm ; in another, 17 miu in length, the length of the head and 

 neck was 0.48 mm . 



