306 



Memoirs of the Indian Museum. 



[Vol. VII, 



o - 37 mm. in diameter. The small, but prominent, cervical papillae are situated at 

 1*2— 1'4 mm., the nerve-ring at 0*4-0-5 mm., and the excretory pore at 1*55-1*9 mm., 

 from the anterior end. 



The tail of the male is about o*6 mm. long. There is a single preanal, sucker- 

 like, fan-shaped aggregation of muscles, situated in front of the long series of oblique 

 caudal muscles (fig. 40). The caudal papillae (fig. 41) are very small and inconspicu- 

 ous. There are ten pairs and an unpaired preanal papilla. Of the postanal papillae 

 Nos. 1 and 2 are close together and ventral; No. 3 lateral. There are three more 

 pairs close together and ventral, and one lateral, just behind the cloaca. The spicules 

 are 1*13 mm. long, and o*i mm. wide dorso-ventrally at the widest part, which is near 

 the root. The accessory piece is well-chitinized, and measures 0'2 mm. in length. 



The tail of the female is o*65-0'8 mm. long, and carries a pair of inconspicuous 

 papillae at 035 mm. from the tip. The vulva is situated at 6'25-7'3 mm. from the 

 posterior end. The vagina is short (about 1 mm.) and nearly straight. The eggs are 

 roundish oval, and measure about 0*075 XO*05 mm. 



The intestine of every specimen examined contained large numbers of diatoms. 



Falcaustra leptocephala, sp. nov. 

 (Fig. 42.) 

 Host: Mahseer (Barbus tor). Locality: Torsa River, Falakata, Eastern Bengal. 

 This species occurred together with the preceding, in large numbers, in the same 



fish. It is easily distinguished from F. 

 barbi by its very narrow head and the 

 absence of a neck. It is a large, stout 

 form, especially as regards the females. 

 These appear an opaque white in spirit, 

 owing to the large numbers of eggs in the 

 uterus. The males, in spirit, remain 

 semi-transparent. In both sexes the 

 intestine shows through the body-wall 

 as a blackish line, and this may be partly 

 due to the fact that its contents, as in 

 the case of F. barbi, consist very largely 

 of diatoms. 



The male measures up to 19 mm. in 

 length and 1*3 mm. in thickness; the 

 female up to 27 mm. and 1 •4-1*8 mm. 

 respectively. The cuticular striations 

 are about 0*002 mm. apart. The diame- 

 ter of the head is o;i-o*i2 mm. The buccal cavity is about 0-05-0-06 mm. long, 

 the pharynx 0-14-0-17 mm. The whole oesophagus, from the head end to the back 

 of the bulb, measures up to 3-5 mm. The bulb is flask-shaped, having no sharp 



Fig. 42. — Falcaustra leptocephala 

 lateral view. 



Tail of male 



