ON THE ANGUILLULID.-E. 97 



LAND AND FRESHWATER'. 



1. MONHYSTEEA'-, Bastian. 



Gex. Char. Body mostly tapering considerably posteriorly. Caudal sucker small, some- 

 what pointed. Iiitc(jument nnstiiated; seta? veiy few; lateral circular mark on 

 either side near anterior extremity. Pharyngeal cavity none. QSsophagiis uniform, 

 cylindrical. Intestinal cells not tessellated. Vulva about posterior third of body. 

 Uterus unsymmetrical. Viviparous or oviparoiis. Spicules long and narrow. Ac- 

 cessory piece, when present, single, small. Ocellus single, often absent. 



In all probability, the two species Avhich I have named 31. disjuncta and M. ambigua 

 will hereafter be found to belong to a distinct genus ; but, not having seen the females of 

 either, I was unwilling to describe them apart, and have therefore placed them tem- 

 porarily in that genus to which they seemed to be the most nearly allied. 



1. M. STAGNALis, u. sp. (Plate IX. figs. 9-11.) 

 Female, length -j^g-", breadth a^o'* 



^External Characters. — Body opaque-white in part, tapering considerably at extremities, 

 especially towards the posterior, which is long and filiform. Head truncated, having a 

 circlet of 4-6 short seta?. Integument plain. 



(Esophagus about ^th of whole length. Intestine narrowed where encroached upon by 

 genital tube, but widening considerably behind vulva. Anus xyy" from posterior ex- 

 tremity. Vulva behind commencement of posterior third of body. Viviparous ; young 

 numerous. Ocellus bright red, on sheath of oesophagus. 



Male, length -^", breadth -4^4". Anus -j^" from posterior extremity. Spicules ^to" 

 long. Accessory piece small, somewhat triangular. Spermatozoa having slight vibra- 

 tile movements, of an elongated oval form, Tifo o ' long. 



Sab. Mud from ponds, Ealniouth and Easthampstead. 



2. M. DisPAK, n. sp. (Plate IX. figs. 1, 2.) 

 Female, length -^3", breadth -5X5". 



Fxternal Characters. — Body scarcely tapering at aU anteriorly, but abruptly behind 

 vulva, and then gradually narrowing so as to terminate with a filiform extremity and 

 minute pointed sucker. Head truncate, provided with 2-4 short setee. Integument 

 hvaline. 



(Esophagus ^^th of total length. Intestinal cells containing rather large dark-coloured 

 particles, having indistinctly tessellated arrangement. Anus X43" from posterior ex- 

 tremity. Vulva about commencement of posterior third of body. 



Hale, not seen. 



Sab. In moss, Falmouth. 



3. M. EmjLARis, n. sp. (Plate IX. figs. 3, 4.) 

 Male, length -oV'j breadth ^-s^". 



' Three exceptions to this, — Rhabditis marina, Monhystera ambigua, and M. disjuncta being marine, and found 

 amongst the sand of tide-pools. " (xoros, single, and larepa, ike uterus. 



VOL. XXV. O 



