648 MR J. T. CUNNINGHAM AND MR G. A. RAMAGE ON THE 



Dodecaceria concharum, Oersted. 



Terebella ostrece, Dalzell, Powers of the Creator, ii. p. 209. 

 Dodecaceria concharum, Oersted, Annul. Dan. Consp., p. 44; Johnston, Brit. 

 Mus. Cat., 1865 ; M'Intosh, Fauna of St Andrews. 



As only one species of this genus is known, a separate diagnosis of genus 

 and species is unnecessary. 



The form is allied to Chaetozone, from which it differs principally in two 

 points — (1) the absence of the peculiar arrangement of setse in the posterior 

 part of the body which characterises Chaetozone; (2) the fact that there are only 

 a few pairs of branchial cirri, confined to the anterior somites. Like Chsetozone, 

 the species possesses a single pair of cephalic cirri, which are thicker than the 

 somatic, and usually twisted spirally. Anterior end of cephalic lobe cylindrical, 

 obtuse, without the annulations seen in Cirratulus. Eyes none ; mouth almost 

 terminal. Posterior part of body considerably thicker than anterior. Colour 

 dull olive-green (PI. XXXIX. fig. 12). 



Habits. — Not uncommon among roots of Laminaria. According to John- 

 ston, it lives in burrows drilled in the shell of Cyprina islandica, but we have 

 not observed it in this condition. 



Fam. ThelethusidjE. 



No cephalic tentacles : parapodia not prominent ; arborescent branchiae on 

 several successive somites. Size large. 



Genus Arenicola, Lamarck. 



Arenicala piscatorum, Lam., Syst. d. Anim. s. Vert., 1802, p. 324. 



Cephalic lobe rudimentary ; tentacles and eyes absent ; proboscis small and 

 soft. Arborescent branchiae commencing some distance behind anterior end; 

 surface of somites marked with transverse ridges and furrows, and shallower 

 longitudinal furrows. Burrows in mud or sand, which it devours. 



Arenicola marina, Malmgren (Linn.). 



Lumbricus marinus, Linnaeus, S. N. xii. 1, 2, p. 1077. 



Arenicola piscatorum, Lamarck, 1802, Syst. d. Anim. s. Vert., p. 234; John- 

 ston, Cat. Brit. Mus.; Cuvier, Regne Anim. ed. accomp. de Planches, 

 Annel., Tab. 8. 



Arenicola marina, Malmgren, Annulata Polychaeta, &c. ; M'Intosh, Fauna 

 of St Andrews. 



Specific Characters. — Branchiae on 7th to 19th chaetiferous somites inclusive; 

 caudal region of considerable length, without chsetae or branchiae. Length, 

 8 inches to 1 foot, diameter about £ inch. 



