176 NEMERTES GRACILIS. 



that Prof. Keferstein published his account of the animal from specimens collected at St. Vaast- 

 la-Hougue. His statement, however, that its mouth is behind the ganglia is erroneous, and it 

 may be remarked that the position of the mouth is more easily seen in this species than usual. 

 The occurrence of three marginal stylet-sacs in some examples is evidently accidental or 

 abnormal. 



The notched condition of the anterior border of the snout, so characteristic of this species, is 

 very conspicuous in a large and flattened member of the Enopla, from New Zealand, in the 

 British Museum. The specimens (in spirit) are about three inches long. 



Sub-Family — Nemertin^s. 

 Proboscis proportionally small. 



Genus IV. — Nemertes, Cuvier, 1817 (Char, emend.). 



Cuvier founded this genus for the description of Lineus marinus, which previously had 

 received other names, and therefore the new title ought to have lapsed. But being set abroad by 

 a zoologist so distinguished, it naturally came to be much employed in describing numerous and 

 often diverse genera, as well as used by subsequent authors as the title of the entire order. 

 Though the genus was first established, therefore, for the reception of one of the Anopla, yet the 

 name has very frequently been bestowed on forms belonging to the Enopla, and, besides, claims 

 attention from its priority, both as a generic title and as applied to one of the typical forms 

 {Nemertes gracilis) of this genus. 



Generic character. — Body more or less elongated, while the proboscis is very much 

 diminished, the anterior region of the organ especially being shortened, so as to cause the central 

 stylet to approach the ganglia. 



1. Nemertes gracilis, Johnston. Plate II, fig. 5. 



Specific character. — Eyes numerous; snout broader than the rest of the body; central 

 stylet of proboscis with an extremely long basal apparatus. Greenish or olive. 



Synonyms. 



1837. Nemertes gracilis } Johnston. Mag. Zool. and Bot., vol. i, p. 534, pi. 17, f. 1. 

 1841. „ „ W. Thompson. Ann. Nat. Hist., vol. vii, p. 482. 



1844. Polystemma gracile, (Ersted. Entw. Plattw., p. 93. 



1846. Prostoma gracilis j Johnston. Ann. Nat. Hist., vol. xvi, p. 435. 



„ Nemertes balmea } De Quatrefages. Ann. des sc. nat., 3 me ser., Zool., torn, vi, p. 197 ; tab. 9, 



f. 3—6 ; tab. 11, f. 2, and 4 ; and tab. 12, f. 2. 

 1849. „ „ Ibid. Voyage en Sicilie, vol. ii, p. 109, pi. 10, f. 6 and 7, and pi. 19, f. 3—6. 



