408 STHENBLAIS BOA. 



Carus in the ( Prodromus Faunae Mediterraneae ' gives the following : — Head with 

 median antenna and generally two short lobulated or fleshy-membranous organs at the 

 base; maxillae well developed; feet all furnished with branchiae, and the anterior pair 

 turned to the front, so that the cirri and setae form part of the cephalic apparatus ; body 

 elongate, vermiform. 



Pruvot and Racovitza l have recently drawn attention to the homologies of the head- 

 processes in Sthenelais, and express the view that the subulate cirrus which springs from 

 the inner side of the bristle-tuft of the first foot (bearing the tentacular cirri) is the lateral 

 tentacle (their lateral antenna). In their descriptions they further point out the exact 

 arrangement of the dorsal and the ventral bristles, the latter forming a horseshoe with 

 the opening in front, and with a spur dorsally and ventrally, each of the latter being 

 characterised by a change in the structure of the bristles. 



1. Sthenelais boa, Johnston, 1833. Plate XXVI, figs. 7 and 8. 



Specific Characters. — Head crimson, broadly ovate, bounded by a nuchal collar 

 posteriorly. Median ridge passes in front into the broad basal process (ceratophore) of 

 the median tentacle, which is short and subulate. Two flap-like organs (ctenidia) occur 

 at each side, the anterior the longer. Two eyes on each side, the larger anterior pair 

 almost hidden by the latter processes, and looking forward and outward. The posterior 

 pair are on the dorsum, a little behind the bases of the processes. A truncated papilla 

 at each side of the head posteriorly. Head fixed to the massive parts of the first feet, 

 which bear externally two tapering cirri of considerable length. Behind the dorsal 

 tentacle is a T-shaped ciliated process. To the inner side of the ventral cirrus of the 

 first pair of feet is a sickle-shaped blunt appendage (ctenidium) — richly ciliated, and 

 probably branchial. A short subulate cirrus (lateral tentacle) exists superiorly on the 

 inner side of the bristle-tuft. The long, subulate, and smooth palpus springs from this 

 basal process, which also carries a double series of long, tapering, slender, spinous 

 bristles. Body elongated, little tapered anteriorly, but gradually diminishing posteriorly. 

 It is rounded dorsally and flattened ventrally, greyish or bluish-green, the latter or flesh- 

 colour characterising the iridescent ventral surface. Segmental eminence at the base of 

 each foot, and a ciliated funnel-shaped process on the foot. Scales 156 pairs ; mostly 

 reniform, and with numerous minute papillae, while the outer border bears a series of 

 large simple papillae. A well-developed branchial process exists above each foot, and on 

 the dorsal ridge beneath it are three T-shaped ciliated organs (ctenidia). The dorsal 

 bristles are long, somewhat stiff and finely tapered, as well as spinous from a little above 

 the base to the apex. Upper set of the ventral bristles with simple tips, boldly spinous; 

 then some with a tapering bifid appendage of about three joints, the end of the shaft 

 having a few rows of spines. The main part of the division, forming the large 

 curve of the horseshoe, has stout bristles with bevelled ends to the shafts, and a short 

 beaked appendage of one segment. Inferiorly the lower spur of the horseshoe has 



1 ' Archives Zoolog. exper./ p. 452, 3 e Serv, iii, 1895. 



