386 Notes from the Gatty Marine Laboratory. 



more tliaii 10 or 12 fathoms' depth, though this is not stated. 

 It is distinguished superficially by the more regular and more 

 definite cuticular ridges anteriorly (PI. XVII. fig. 2), by the 

 more elongated and more acute head, by the smoother and 

 more glistening body throughout the posterior region, by the 

 presence of two sets of cuticular ridges towards the tail, two 

 occurring a little in front of the caudal hump and four on the 

 edge of the downward slope to the caudal process, which 

 generally agrees with that o£ Ophelia limacina, while 

 differing in detail. The mouth is more posterior in position 

 than in 0. limacina, and the anterior region, viz. that in 

 front of the cirri, is considerably longer. The cirri are much 

 longer and have a warty aspect, from little papillfe or eleva- 

 tions — it may be due to extravasations. On the other hand, 

 the bristles are less developed, a feature conspicuous poste- 

 riorly in 0. limacina, where they form a fringe on each side 

 of the dorsal groove of the caudal process. No well-marked 

 groove occurs on the dorsum of this process in 0. radiata, and 

 the process itself is shorter. Ventrally both are deeply 

 grooved to the tip, but the two ventral cirri of 0. limacina 

 are considerably smaller and terminated by two clavate or 

 button-like processes, whereas the ventral cirri of 0. radiata 

 are broadly ovate flattened processes, conical posteriorly, and 

 ending in a simple very slightly tapered filament (PI. XVII. 

 fig. 4). Delia Chiaje shows fourteen cirri, forming the upper 

 arch of the tail, whereas Claparede * describes and figures 

 only eight. On the other hand, Baron de St. Joseph f gives 

 sixteen, including, however, the two median ventral, in his 

 differentiation of the species from Ophelia neglecta. In the 

 present example five occur on each side and a median cirrus 

 dorsally, so that the total number is eleven % (Ph XVII. 

 fig. 3). This species is the common one at Naples, and the 

 sexes are distinguished by colour, the males being pale. The 

 ova are greenish. Claparede gives considerable attention to 

 its structure in the work just referred to, and puts a different 

 interpretation on the diverticula on the dorsum of the 

 oesophagus from that given by several of his predecessors, 

 who varied in interpretation from salivary glands and respi- 

 ratory organ to heart. This muscular organ he associated 

 with the stiffening of the snout by the perivisceral fluid 

 during its boring in the sand and muddy sand. De St. 



* Annfl. Chetop. Naples, p. 284, pi. xxvi. tig. 1 c. 

 t Ann. Sc. Nat. 9^ ser. t. iii. p. 231 (1906). 



X The artist makes seven on each side of the median. It has not been 

 possible to check these figures before publication. 



I 



