ON THE ANGUILLULID X. 135 
curved, tooth-like projections from its inner surface. Csophagus not distinctly 
muscular, cylindrical, and almost uniform in size; surrounded by a distinct «@so- 
phageal ring. Intestine mostly covered with olive-coloured particles, having a 
tessellated arrangement. Vulva at centre of body, or occasionally at posterior third. 
Uterus symmetrical or unsymmetrical. Spicules two, with or without a single 
accessory piece. Ocelli mostly wanting. Exeretory ventral gland simple, tubular, 
extending from the anterior third nearly to the termination of esophagus. Lateral 
canals often distinctly cellular. 
Movements active. 
This is not quite so natural an assemblage as those presented by some of the other 
genera, even after the freshwater species formerly included by Dujardin have been 
transferred to the genus Mononchus. ln some members of this genus Oncholaimus the 
vulva is posterior, and the uterus unsymmetrical; and in some males also the spicules 
are solitary, whilst in one at least, O. vulgaris, there is a large and well-developed 
accessory piece. Owing to my not having found in several cases both the male and 
female representatives of the same species, I am unable to say, from my own observa- 
tion, whether these alterations in the male and female organs are generally coincident, 
and constant enough to enable the species to be ranged under two distinct subgenera ; 
and, unfortunately, the details concerning the anatomy of those discovered by other 
observers are too scanty to afford any assistance in the solution of this question. In 
two species also, O. fuscus and O. albidus, Y have been unable to detect the usual 
esophageal ring. 
l.O.vurcARIs, n.sp. (Plate XI. figs. 126-198 a.) 
Female, length 4”, breadth 1”. 
External Characters—Body elongated, cylindrical, tapering very slightly at extre- 
mities. Sucker well developed, with three large sucker-tubes occupying nearly the 
whole of the cavity of body posterior to anus. Head truncate, with a circlet of 4-6 
short, stout setze, and a few smaller ones scattered over anterior part of body. Integu- 
ment thick, with an appearance of longitudinal markings zogo apart; integumental 
pores distinct in mid-dorsal and ventral regions. 
Pharyngeal cavity Az” long by gts” broad, having three strongly marked, slightly 
curved teeth proj ecting into cavity. Œsophagus about 4th of total length, nearly uniform 
In size, having three longitudinal rows of pigment-granules; embraced at termination of 
anterior third by an æsophageal ring. Intestine broad, having a thick coating of olive- 
coloured hepatic granules, enclosed in cells, and presenting a distinct tessellated arrange- 
ment, Anus 14” from posterior extremity. Vulva slightly posterior to middle of 
body. Uterus bifid. Exeretory ventral gland opening close to the esophageal ring. 
Lateral canals distinct, cellular. 
Male, length -%”, breadth 2”. 
Anus 5X5" from posterior extremity. Spicules rather wider at middle, and tapering 
towards extremities, +45” long. Accessory piece single, somewhat triangular, 737° long 
by ste” broad at the base. A large mid-ventral prominent sucker 137 above anal cleft. 
