ARICIA CUVIEEL 497 



organ in a small nnmber of the anterior segments only (4 — 5 to 13 — 15), whilst the lateral 

 ciliated organs occnr in every segment. The otocyst is situated at the base of the dorsal 

 cirrns and opposite the ciliated organ in the form of a diverticulum of considerable depth. 

 Its walls have thick cuticle without cilia, and the surrounding cells are finely granular 

 and stain deeply, and their extremities are fibrillar. Thus two sense-organs occur in the 

 Ariciidae, viz., the ciliated organs and the otocysts. 



Hacker (1896) includes the Ariciidge amongst those with non-pelagic larvas, and he 

 alludes to a six days' old larva of Aricia faetida, described by Salensky, 1 with three ciliated 

 rings in addition to the cilia of the prototroch. 



Kostanecki 2 subjected the eggs of Aricia to an acid solution (acetic and nitric), and 

 then to a hypertone solution, with the result that certain ova segmented into three or 

 four blastomeres, and a few reached the six- to eight-celled stage. 



An interesting memoir lately published by Ceruti 3 places the genera Aricidea and 

 Paraonis on a proper footing, and demonstrates that they pertain rather to the group of 

 the Spionidse than to the Ariciidse. This group will subsequently be dealt with. 



The distribution of the Ariciidge is still in need of elucidation, but certain European 

 forms would appear to stretch to the eastern American shores, where, under new names, 

 it is not always easy to identify them. Some are littoral, whilst others frequent water -of 

 considerable depth. 



Genus LXXVII. — Aricia, Sayigny, 1820. 



Head pointed, without tentacles ; mouth with a foliaceous proboscis. Body more or 

 less elongated, flattened dorsally and rounded (convex) ventrally, little tapered anteriorly, 

 but slender posteriorly, and ending in two slender caudal cirri. Regions of the body 

 two, the anterior with rudimentary feet and peculiar spines, the posterior with dorsal and 

 ventral divisions better developed. Branchiae commence about the fifth foot, and 

 continue throughout. Bristles club-shaped serrated forms and peculiar serrated (came- 

 rated) forms with tapering tips. Body-wall as in the family. 



1. Aricia Cuvieri, Audouin and Edwards, 1833. Plate LXXVI, figs. 5-5 c — feet; Plate 

 LXXXY, figs. 7-7 b— bristles; Plate LXXXVII, fig. 18— body. 



Specific Characters. — Head a short pointed cone without trace of rings or eyes. 

 A transverse line separates it from the peristomial segment ventrally, but dorsally 

 a crescent is cut from the latter at the base. Body slightly diminished in front, gradually 

 tapering posteriorly and reaching eight or more inches in length. It is flattened dorsally 

 and rounded on the ventral surface anteriorly. Segments narrow. In transverse section 

 dorsally it is concave anteriorly and flattened posteriorly ; convex ventrally. Peristomial 

 segment narrow dorsally, but broad ventrally. Proboscis forms in extrusion a frilled 



1 ' fitud. Devel. Annel./ i, taf . vii, fig. 8, a, v. 



2 e Journ. R. Micros. Soc./ 1909, p. 575 (from 'Bull. Intemat. Acad. Sc. Cracovie,' 1909, pp. 

 238—253, 16 figs.). 



3 c Mitth. Zool. Stat. Xeapel./ Bd. xix, pp. 459—512, Taf. xviii and xix, 1909. 



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