856 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [138] 



continued posteriorly into a collar which incloses the anterior part of 

 the body, in alcoholic specimens often transversely wrinkled. Probos- 

 cides nearly equaling the bothria in length, armed with short, strongly 

 recurved hooklets, sheaths nearly straight with a single spiral turn im- 

 mediately in front of the contractile bulbs. The latter are long-oval, 

 and a little more than one-half as long as the bothria. The body begins 

 immediately behind the contractile bulbs, and is at once crossed by 

 transverse lines which soon outline distinct segments. The first seg- 

 ments are very much broader than long. Subsequently they increase 

 in length slowly, the posterior mature segments becoming at first squar- 

 ish, then a little longer than broad. Male genital apertures marginal, 

 irregularly alternate, near anterior edge. Cirrus small, smooth ; cirrus 

 bulb slender. Female genital aperture lateral(?). 



Ova small, very abundant, nearly spherical, about 0.01 6 mm in diam- 

 eter, and with a thin shell. 



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

 1887, Wood's Holl, Massachusetts. 



The general habit of T. robustum is stouter than T. tenue. The head, 

 neck, and segments are relatively broader; the head is more blunt at 

 the apex; the proboscides emerge from the apex of the head instead of 

 a little way back of the apex ; the hooklets on the proboscides are much 

 stouter and more sharply recurved ; the contractile bulbs are longer; 

 the cirrus opens near the anterior end of the segment instead of near 

 the middle. 



I have found this species associated with T. tenue, as follows : August, 

 1884, two specimens; August 1, 1887, two specimens; August 8, frag- 

 ments ; August 10, one specimen. 



The following measurements were obtained from alcoholic speci- 

 mens: 



Dimensions. 



Length 



Length of bothria 



Breadth of head 



Length of head and neck 



Diameter of neck 



Length of proboscides 



Diameter of proboscides 



Length of hooklets 



Breadth of hooklets 



Length of contractile bulbs 



Breadth of contractile bulbs 



Length of anterior segments, approximate. 



Breadth of anterior segments 



Length of posterior segments 



Breadth of posterior segments 



No. 1. 



mm. 

 20.00 



0.68 



0.70 



1.20 



0.50 



0.60 



0.03 



0.011 



0.005 



0.33 



0.10 



0.02 



0.38 



0.52 



0.96 



No. 2. 



mm. 

 24.00 



(i.60 



0.64 



1.18 



0.42 



0.60 



0.03 



0.014 



0.005 



0.32 



0.08 



0.02 



0.40 



0.86 



0.80 



The booklets are nearly uniform in shape, which is much like that of 

 the claw of a cat. The breadth of base equals about half the length. At 



