626 W. M. SMALLWOOD AND ELIZABETH G. CLAEK 



lateral halves by a longitudinal furrow. The walls of the buccal 

 cavity are chiefly composed of muscles and are greatly thickened 

 ventrally. The entire mass is cylindrical (fig. 2, phx.). 



The radula, borne upon the rounded prominence forming the 

 floor of the buccal cavity, is folded in the middle and fits into the 

 longitudinal groove ; it emerges from the curved sac which lies 

 at the ventro-posterior angle of the buccal mass. This sac is 

 lined with cells whose special function is the secretion of new teeth. 

 The total number of rows of teeth is 95 to 100; of these 20 to 30 

 are in the radula sac, the posterior 4 to 5 being in process of forma- 

 tion. The median tooth is absent. In each transverse row are 

 165 to 170 teeth on each side. All of the pleural teeth bear two 



Fig. 1 Chromodoris zebra Heilprin. Viewed from the right side ; the branchial- 

 rosette turned toward the observer; f natural size. Copied from Smallwood, '10. 



denticles; one long denticle terminating in a sharp slender point, 

 and a shorter one with a slightly blunter distal end (fig. 3). 

 Slight variations in size and form of teeth occur, as may be seen 

 in figure 3, and as they near the margin, we find that the 

 denticles gradually become more and more blunt, until at the 

 outermost edge, they are mere rounded knobs supported by the 

 broader base. In some teeth, the denticles are entirely lacking, 

 doubtless having been worn off. The posterior margin of the 

 tooth, that is, the side toward which the denticles point, is slightly 

 crenulated. All teeth are of nearly the same size, measuring 20 

 micra long, 9 micra wide, and 3 micra thick. The longest denticle 

 measured was 6 micra long. 



Bergh (78, pp. 23, 29 and 30) gives the following for Chromo- 

 doris villafranca: 



Forma corporis gracili.s. Pedamentum folioriim branchialiiim humile. 

 Color paginao supcrioris glaucescens, fasciis transversalibus latioribus 

 caeruleis dilutis et praesertim lineis fulvis (ut plurimum 7) non semper 



