ON THE ANGUILLULID X. 101 
this type; whilst I have transferred the freshwater members to my new genus Monon- 
chus. The species of this latter genus differ from, those of the former in having one 
pharyngeal hook only instead of three; in having the head sometimes furnished with 
papillæ, but never, as far as I have seen, with sete; by the different structure of the 
esophagus, and absence of the peculiar œsophageal ring; and, lastly, by the compara- 
tively undeveloped condition of the caudal sucker and its appendages. 
The males of this genus must be either very minute or very scarce; for though I 
have seen nearly one hundred female representatives of the different species, I have 
never met with a single specimen of the opposite sex. 
1. M. TRUNCATUS, n.sp. (Plate IX. figs. 25, 26.) 
Female, length 45", breadth +5”. 
External Characters.—Body tapering slightly anteriorly, but more considerably pos- 
teriorly. Head truncate ; no papillæ. Integument with longitudinal striæ, 755" apart. 
Pharyngeal cavity oval, 535$” in length, with a single hook projecting from upper 
surface. (Esophagus about ith of total length. Intestinal cells with light-coloured 
particles, having distinctly tessellated arrangement. Anus 113 from posterior extre- 
 mity. Vulva slightly posterior to middle of body. Lateral canals broad, very indis- 
tinet, only recognizable behind intestine; no cells apparent—merely a few light-coloured 
scattered granules. | 
Male, not seen. 
Hab. Small pool amidst decaying moss and liverwort, Falmouth. 
2. M. PAPILLATUS, n.sp. (Plate IX. figs. 27, 28.) 
Female, length 44", breadth 415". | 
External Characters.—Body opaque-white in colour, tapering slightly anteriorly, but 
gradually to a point posteriorly. Head truncate; mouth surrounded by four well- 
marked papillæ. Integument with longitudinal strive, about 19000 apart. 
Pharyngeal cavity a little removed from anterior extremity, proportionally rather 
small, 7147” long; tooth single. Œsophagus ith of total length. Intestinal cells con- 
taining yellowish-coloured granules. Anus 745” from posterior extremity. Vulva at 
commencement of posterior third of body. Uterus bifid. 
Male, not seen. : 
Hab. Between the sheaths of the leaves, at the lower part of culm of Festuca elatior, 
Broadmoor, Berks, | 
3. M. macrostoma, n.sp. (Plate IX. figs. 29, 30.) 
Female, length 455", breadth 414". - à 
External Characters.—Body tapering very slightly towards head, more considerably 
Posteriorly , where it is filiform for a short distance. Head obtusely rounded, with two 
papillz, upper and lower. Integument with longitudinal strize. 
Pharyngeal cavity large, 51” long; hook single, 5 long. Œsophagus about ath 
of total length ; very slightly increased in size posteriorly, where also there is a di- 
