156 MR. H. CHARLTON BASTIAN’S MONOGRAPH 
the posterior, which is sharp and filiform. Head bluntly rounded, furnished with a circlet 
of 4-6 short set». Integument having very fine transverse striæ, about 35555" apart, 
Pharyngeal cavity very small, conical. (Esophagus about th of total length, en. 
larging very slightly backwards. Intestine sparingly covered with non-tessellate he. 
patic granules. Anus 555 from posterior extremity. Ocelli two highly refractive yel. 
lowish bodies, with a dark central spot on dorsal aspect at 3000 from anterior extremity, 
Vulva behind centre of body. 
Male, length 4", breadth 555. 
(Esophagus relatively shorter. Anus 543” from posterior extremity. Spicules barbed 
at upper extremity, curved, 1900 long; accessory pieces lying nearly at right angles 
to spicules, pointed. 
Hab. Small green filamentous weed from tide-pools, Falmouth. Also observed ina 
small aquarium for two or three weeks, feeding on minute vegetable spores near the 
surface of water. 
2. T. PARVUS, n. sp. (Plate XIII. figs. 185, 186.) 
Female, length 4", breadth 1350 - 
External Characters—Body tapering at both extremities, especially at posterior, 
commencing behind vulva. Head truncate, naked. Striæ of integument imperceptible. 
Pharyngeal cavity indistinct. Œsophagus about +th of total length. Intestine 
sparingly covered with hepatic particles. Anus 345" from posterior extremity. Vuloa 
posterior to middle of body. Ocelli...... 
Male, not seen. 
Hab. Small green weed from tide-pools, Falmouth. 
23. THERISTUS!, Bastian. 
GEN. CHAR. Body tapering at extremities. Caudal sucker small; sucker-tubes not 
visible. Integument having transverse strie; lateral, circular, convex prominences 
close to anterior extremity; cephalic setæ, but no papille. Pharyngeal cavity 
moderately large, rounded ; parietes membranous, not horny. (Esophagus distinctly 
muscular, nearly cylindrical. Intestine plentifully covered with hepatic particles, more 
or less tessellate, and of a brownish colour. Vulva at commencement of posterior 
third of body. Uterus unsymmetrical. Spicules shaped like a reaper’s hook. At 
cessory pieces two thin rounded plates directed backwards. Ocelli none. Vaginal 
glands two, unequal, pyriform. Exeretory ventral gland . . .. Lateral canals ..' 
Movements very active. 
1. T. ACER, n. sp. (Plate XIII. figs. 187-188.) 
Male, length 4,5", breadth 41". 
External Characters.—Body tapering at extremities, slightly forwards, but gradually 
narrowing to a point posteriorly. Head rounded, furnished with about eight spreading 
sotse, qu from swollen bases., Integument having transverse striæ, 13000 apart 
conical projections 3345” in diameter, at 1350 from anterior extremity. 
! Oepioris, a reaper, on account of the shape of the spicules. 
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