MORPHOLOGY OF THE AMPHINEURA. 213 



Chffitodermata and Neomenise instituted by v. Jhering can be 

 retained. As to the generic names, the manuscript name of 

 Solenoj}us, Sars, which was given to the specimens in the Bergen 

 Museum, but which was never pubHshed, and which Koren and 

 Danielssen (11) nevertheless retain for JVeotnenia, TuUberg, will 

 once for all have to be abandoned, when it is remembered that as 

 early as 1826 the name Solenopus was pre-occupied in zoology, 

 C. J. Schonherr having in that year assigned it to a genus of 

 Curculionidae, Coleoptera on p. 268 of his work ' Dispositio 

 methodica,' &c. Up to the present day the genus Chcetoderma, 

 Loven (14), counts one species [Chatoderma nitidulum,, Loven = 

 Crystallophrysson nitens, Mobius) ; Proneomenia, Hubr. (7), 

 one (P. sluiteri) ; Neomenia, Tullb. (28), eight, Neomenia cari- 

 nata, TuUberg, Neoynenia affinis, dalyelli, incrustata, margari- 

 tacea, lorealis, sarsii (all Koren and Danielssen's) , and Neomenia 

 gorgonophila, Kowalevsky. Neomenia corallopJiila, Kowalev- 

 sky, has not been described as yet, although it is mentioned in 

 his explanation of plates (13). I agree with v. Jhering in 

 thinking it probable that Koren and Danielssen's species will 

 perhaps come to be reduced in number when these investigators 

 have examined their specimens more in detail ; external shape 

 and size must be looked upon as very misleading specific 

 characters in these animals. Neomenia sarsii and N. gorgonophila 

 will perhaps prove to be Proneomenias. 



Of the great number of species and genera amongst the 

 Chitones every text-book on conchology can give evidence; it 

 would lead us too far to enter into any details in this respect. 

 Especially of the genus Chitonellus, as will be shown below, a 

 more detailed examination of the different species promises to 

 yield interesting results. 



B. Integument. — In all the Amphineuea a thin cellular layer, 

 which rarely appears to exceed one cell in thickness (3, 7, 11, 

 13, 18, 22), is appUed upon the muscular tissue of the body-wall, 

 and fulfils the function of matrix for the integument. In Chiton 

 it is also continued upon those membranous portions of the body- 

 wall which are found in the duplicatures containing the shells. 



The integument furnished by this matrix is composed of two 

 elements : 



a. A cuticular substance of varying thickness (thickest pro- 

 bably in Proneomenia^. 



h. Calcareous elements deposited within this cuticle, and 

 either forming spicules only (Soleuogastres), or spicules and 

 plates or shells (Chitones) . 



Structures which may to a certain extent be regarded as 

 transitional between the two are the horny or chitinous bases of 

 certain spicules (18), and still more those horny hairs or setae 



