186 AONIDES OXYCBPHALA. 



could compare only with those of Polyodontes maxillosus. He considered that it showed 

 more affinities with Polydora than with the other Spionidse. 



The Spiophanes Kroyeri of Grube l (1860) from Greenland is a different form, having 

 a structure anteriorly approaching that of Prionospio, at any rate, with four pairs of 

 branchial (?) lamellae in front. 



The Spiophanes cirrata of Sars 2 (1873) differs very slightly from this form, the chief 

 characteristics being the presence of more than one spike above the main fang of the 

 hooks, and the equal anal cirri. The British form has the frontal tentacles more distinct, 

 and the cirri seem to be somewhat longer both anteriorly and posteriorly. Much, how- 

 ever, depends on the condition of the specimen and its preparation, and two forms so 

 closely allied need further investigation. 



Mesnil (1896) found the pelagic larvae of this species abundant at Wimereux in 

 August, and it has long been known at St. Andrews. Mesnil recognises them by the 

 absence of black pigment, and the presence of yellowish and orange pigment, especially 

 on the prostomium and perianal ring. In the earlier larvae of nine or ten segments the 

 snout is smoothly rounded, but when twelve segments are present the frontal processes 

 and tentacles appear, with two pairs of eyes. They are flanked by tufts of long, 

 glistening, provisional bristles, which diminish from before backward. He observed the 

 precursors of the kC organes en filieres " from the fifth to the eleventh segments. In seti- 

 gerous segments five to seven is a refringent kidney-shaped mass with two cilia, which 

 the author considers to be the precursor of the glandular pouches or " organes k filiere." 

 The anal region has four short appendages. 



This author specially alludes to Olaparede's " organes en filiere" in the adult from 

 the fifth to the fifteenth segment in this species, as composed of minute granular cells 

 which split into thirty chitinous threads, the outer end of which touches the surface 

 between the dorsal and ventral divisions of the foot. He states that they are mobile, 

 after the manner of a brush. 



Michel 3 (1898) gives an account of an example which had an oblique bud anteriorly, 

 and five rings were abnormal. 



Genus C. — Aonides, Claparede, 1863. 

 Prostomium forming an acute cone. Branchiae commencing on the second setigerous 

 segment, and terminating abruptly in the anterior third of the body. Dorsal lamellae 

 distinguishable from the branchiae. Anal cirri. Dorsal winged hooks commencing before 

 the ventral. 



1. Aonides oxycephala, Sars, 1861. Plate XCVIII, figs. 9— 9 e— feet and tail; Plate 



C, fig. 7— posterior foot; Plate CV, figs. 10— 10 6— bristles and hook. 



Specific Characters. — Head forming an acute cone, the central ridge passing backward 



to terminate in a small occipital tentacle. Four eyes, two on each side of the ridge in a 



transverse line just in front of the tentacles. About four inches in length and having 



1 ' Archiv f. Naturges./ 1860, p. 88, Taf. v, fig. 1. 



2 'Bidrag Christ. Fauna/ p. 68, Tab. xviii, figs. 1—16. 



3 ' Bull. sc. Fr. Belg./ 4 e ser., t. xxxi, p. 245. 



