SYNOPSIS OF FAMILIES, GENEBA, AND SPECIES. 135 



Genus II. Tetrastemma, Ehrenberg. — Eyes four; arranged so as to indicate a square or oblong. 



1. T. melanocep/iala, Johnston. — A large black pigment-mass between the anterior and pos- 



terior pairs of eyes. Marginal stylet-sacs placed somewhat in advance of the central 

 apparatus. 



2. T.Bobertiance, n. s. — Head furnished with a brown collar, which sometimes hides the posterior 



(smaller) pair of eyes. Body longitudinally striped with two brown and a median white 

 line. 



3. T. Candida, 0. F. Miiller. — Head flattened, wider than the rest of the body ; eyes distinct. 



Stylets large. Pale yellow, greenish or reddish brown. 



4. T. vermicula, De Quatrefages. — A longitudinal dark patch between (and connecting) the eyes 



of the respective sides. 



5. T.flavida, Ehrenberg. — Head not wider than the rest of the body. Anterior and posterior 



pairs of eyes widely separated. 



6. T. dorsalis, Abildgaard. — Body short, thick and rounded ; speckled with yellow and brown j 



sometimes with a pale median stripe on the dorsum. 



Genus III. Prosorhochmus, Keferstein. — Eyes four ; not forming a square. Snout dimpled and 

 furnished with a transverse superior lobe. Ovo-viviparous. 



1. P. Claparedii, Keferstein. — Snout blunt; eyes placed far back, the space between the anterior 

 pair being widest. Yellowish. 



Sub-Family, NEMERTIN^. 



Proboscis proportionally small. 



Genus IV. Nemertes, Cuvier. — Body more or less elongated, while the proboscis is very much 

 diminished, the anterior region especially being shortened so as to cause the stylets to 

 approach the ganglia. 



1. N. gracilis, Johnston. — Eyes numerous. Snout broader than the rest of the body. Central 



stylet with a very long basal apparatus. Greenish or olive. 



2. If. Neesii, (Ersted. — Eyes numerous. Stylets short and grooved. Streaked on the dorsum 



with purplish brown. 



3. If. carcinophila, Kolliker. — Eyes two. No marginal stylet-sacs. Body pinkish. 



