CESTODE PARASITES. 261 



Head. — The head is somewhat cubical iu general shai)e. It is divided into four bothridia, which 

 are sessile for the greater part of their lengtli, only the terminal quarter or so being free. Each bothridium 

 is divided into tlu'e.e loculi by two transverse septa. The lociili decrease regularly in size from the 

 proximal one, which is the greatest. The loculi are rather shallow, and their lips and edges are broad in 

 proportion to the area they enclose. A pair of bifurcated hooks overhang the proximal loculus of each 

 bothiidium. They are stout, brown, hollow structures, strongly curved. The two spines whicli compose 

 a pah of hooks are united at their bases. The spines which are nearest to the longitudinal median Une in 

 each bothridiimi are very slightly larger than the outer ones. The degree of curvature appears to be 

 the same in all the hooks. They are exactly like the hooks of Acanthohothrium (Calliobothrium) crassi- 

 colle, Wedl., figured by Zschokke (26, Plate 5, Figs. 93 and 94), but are much smaller. Above the four 

 hooks each bothrium is provided with a smaU but well-marked accessory sucker, which is situated on a 

 small knob-like projection. The neck is long and irregular in diameter. Its cuticle is very strongly 

 wrmkled transversely, and it mei-ges imperceptibly into the strobila. 



The proglottides are remarkable, in that they are aU broader than long. Over 200 proglottides 

 were counted. Their sides are slightly convex, and their edges are saUent. The greatest width of the 

 strobila is anterior to its termmation, the riper proglottides becoming slightly narrower. The worm is 

 oval in transverse section. The cuticle is transversely WTinkled in the latter two-thirds of the posterior 

 proglottides. Well-defined bands of longitudinal muscles can be seen to run through the worm. 



The genital jjores are lateral and irregularly alternate, the average being about four on the left 

 side, then four on the right side. 



The oirrhus is fairly long, bulbous at the base, but tapering towards the termination, and can be 

 seen to be hollow. No internal structure can be observed without sectioning, owing to the extreme 

 opacity of the worms. Several specimens when slightly pressed. under a eover-shp extruded large masses 

 of ova. These ova are very minute, being about 0-025 mm. in diameter. They consist of a clear 

 spherical cell with a large granular nucleus. A number of calcospherules are irregularly dotted about 

 on the periphery. 



The diagnosis of Acanthobothrium herdmani, n. sp., is as foUows : — 



Stout opaque worm, 63 mm. long and 2 mm. broad. Oval in cross section. Head almost square, 

 and comparatively small. The four bothridia are sessile for the greater part of their length. Each both- 

 ridium is divided bj' two transverse septa into three locuh, whicli regularly decrease in size from the 

 proximal end, and is also sm-mounted by a pair of bifurcated hooks, proximal to which is a small sucker. 

 Neck long and somewhat irregular in diameter. Proglottides always broader than long, their sides being 

 slightly convex, and their edge? not saUent. Genital pores marginal and irregularly alternate, averaging 

 four on the left side, then four on the right side. 



Habttat. — The spiral valve of Trygon kuhli, Miill. and Henle. Fifteen specmiens. Clieval Paar. 

 November and December, 1910. 



Following Luiton, I have here adopted Van Beneden's classification in separating the genera 

 Calliobothrium and Acanthobothrium, the latter genus being marked by tlie presence of bifurcated hooks, 

 and tlie former genus by simple hooks. Accordmg to this classification Calliobothrium farmeri, South- 

 well (23), becomes Acanthobothrium farmeri. This classification, however, is not adopted by Zschokke. 



Acanthobothrium herdmani, n. sp., closely resembles Acanthobothrium crassicdle, Wedl. The 

 hooks are exactly similar, but are much smaller in Acanthobothrium herdmani, n. sp. Our specimens 

 further differ from Acanthobothrium crassicolle, Wedl., in being four times larger, and in the size and 

 shape of the scolex and areolas. 



I have pleasure in naming our specimen in honour of Professor Herdman, whose kindly help and 

 assistance I here gratefully acknowledge. 



Professor Shipley (21 . page 343) remarks that " A point of interest in the Holmmthology of 

 Elasmobranchs is the minuteness of the parasites. As Dr. Orly records, the tapeworms which infect 

 the largest sharks, such as Carcharias and Heptanchus, never surpass 10 cms. in length. As a rule, the size 

 of the Entozoon is inversely proportional to that of its Elasniobranch host. Both tlio smaU size and the 



