4 AsHWORTH & HOYLE, Species of Ctenopteryx. 



In regard to these several points our example presents 

 the following appearances : — 



1. The pectinated fin extends practically the whole 

 length of the mantle. The ceasing of the fin behind the 

 anterior margin of the mantle in Appellof's type we 

 regard as due to its immaturity : a similar condition is 

 seen in several other young examples which have come 

 into our hands. 



2. The pectinated fin has 23 teeth on the left and 24 

 on the right side. On the specimen from Monaco which 

 appeared to be best preserved we only succeeded in 

 counting 24 teeth on each side, but it is by no means 

 easy to be sure of the number owing to the unsatisfactory 

 state of preservation. 



3. The fin is very narrow posteriorly, but is continuous 

 round the hinder end of the mantle. Here, again, we 

 attribute the deficiency in Appellof's type to immaturity. 

 In seven young examples examined by one of us, ranging 

 from about 4 mm. to 9 mm. in length, the fins are clearly 

 separate from each other, though in one or two cases 

 there is only a short interval between them. 



4. The tentacles are somewhat longer than the mantle : 

 their excessive length in the types of C. cyprinoides we 

 attribute to the maceration which they have undergone. 

 This elongation of the tentacles is of very frequent occur- 

 rence in cephalopods taken from the stomachs of cetaceans. 



5. This character we do not regard as of any 

 systematic importance. The extent to which the head 

 is drawn into the mantle varies greatly in different 

 examples of the same species and depends on the state 

 of contraction of the retractor muscles at the time of 

 death. The diameter of the head in relation to the size 

 of the opening of the mantle is also dependent on the 

 state of contraction of the latter. 



