22 SIR CHARLES ELIOT. 
larger than the line of the cerata, and the reddish ramifications are clearly visible 
through the skin. The diverticula within the cerata, on the other hand, are only 
visible with difficulty, being of the same colour as the integuments as preserved. 
In structure they are similar to the same organs in . gigas. 
Fic. 24,—Notaeolidia depressa—a First LateraL Toorx; 6 SECOND; c THIRD; d Fourrs. 
The reproductive system is not much developed, and the animal, considering 
its relatively small size, is probably sexually immature. The follicles of the 
hermaphrodite gland lie among the hepatic branches, but do not form a thick mass 
above them, as in M. gigas. The anterior genital mass is small and yellow, the 
spermatotheca of moderate size and roundish, the vas deferens long and much 
convoluted. 
CRATENIDAE. 
(See Eliot, Jour. Mar. Biol. Assoc., VII. (1906), pp. 363-366.) 
THE division into genera of the forms comprised in Dr. Bergh’s family Cratenidae is a 
matter of great difficulty. Phestilla is distinguished by its dentition among other 
points, and Hervia by its elongate shape; but Cuthona, Cuthonella, and Cratena are 
not easily separated from one another. None of them have any very remarkable 
characteristics; they are smallish AMolids, neither very long nor very stout, with 
simple rhinophores, cylindrical cerata, a foot rounded in front or with inconspicuous 
projections, and teeth of the common horse-shoe shape, bearing a moderate number of 
denticles (usually less than twelve) on each side of a central cusp. 
In Jeffreys’ ‘‘ British Conchology,” Vol. V., Alder divided many of the forms 
comprised in these genera between Cuthona, having the branchie close set, and Cavolina, 
having them in rather distant rows, and also having the central cusp of the teeth a 
little prominent. But the name Cavolina is preoccupied, and the difference between 
close set and distant rows is one of degree, which may be obscured in preserved 
specimens. According to Dr. Bergh’s definition, the difference between Cuthona A. and 
H. and Cratena Bergh is very slight. The former has caput latum .. . podarium 
antice rotundatum, the latter, caput non latum, podarium antice leviter arcuatum. 
Cuthonella Bergh is more distinct. The foot has pointed corners in front, the 
jaws bear several series of denticles, the anus is latero-dorsal, and the otocysts 
