36 THE VOYAGE OF H.M.S. CHALLENGER. 



Garnoti, Bl. Peru. Ch. Danielli, Con. Illust., f. 48, which comes from the Cape of Good 

 Hope, may prove to be a distinct' species, but all our specimens are much worn." I 

 have no means for deciding whether Acanthochiton hirudiniformis is a synonym of Acan- 

 thochiton garnoti, but Gray 1 is almost certainly incorrect in making Acanthochiton 

 zelandica, Quoy and Gaim., a synonym. I am not acquainted with "Acanthochiton 

 hookeri, Gray, Dieffenbach, p. 262." 



H. — Cryptoidea. 

 No representatives of the Cryptoidea were collected by the Challenger Expedition. 



I. — CfllTONELLOIDEA. 



As there exists a certain amount of uncertainty concerning the generic subdivisions of 

 this group, the following account may perhaps tend to elucidate the subject. 



Burrow 2 published a description of Cryptoconchus larvcsformis, an unpublished name 

 which Blainville bad given to a species in the British Museum, and of which one specimen 

 is still extant (fide E. A. Smith). 3 The generic name of Cryptoconchus was at the same 

 time given to Cryptoconchus porosus, Blainville, and the latter being generically distinct 

 from Cryptoconchus larvmformis retains the generic appellation ; being the first of the 

 two species described and more answerable to the name. 



Blainville 4 says, " Cryptoplax (Moluscart.) : Sous-genre del'ordre des oscabrions, etabli 

 par M. H. de Blainville, dans le supplement a l'Encyclope'die d'Edimbourg, pour des 

 especes qui ont tons les principaux caracteres de ce genre, mais chez lesquelles le corps, 

 etroit alongd," &c. &c. But he does not refer to the name Cryptoconchus in Burrow's 

 Elements. He says only two species are known, " Cryptoplax larviformis " and " Crypto- 

 plax depressus ; " and continues, " Dans ces deux especes, dont on ignore la patrie il y a 

 de chaque cote' du dos une se'rie de faisceaux de soie parfaitement symdtriques." I have 

 been unable to find the Encyclopaedia article referred to, and Mr E. A. Smith informs me 

 that he is unable to determine what is the Cryptoplax depressus of Blainville — it may be 

 Choneplax strigatus, Sow. 



Lamarck 5 describes Chitonellus IcBvis and Chitonellus striatus. To which Deshayes 

 added in the second edition, 6 Chitonellus fasciatus, Quoy and Gaim., and Chitonellus 

 oculatus, Quoy and Gaim. 



1 Froc'Zool Soc. Lond., 1847, p. 70. 

 The Elements of Conchology, 1815, p. 191. 



3 Eep/Zool. Collect. H.M.S. "Alert," 1884, p. 86. 



4 Dict'desISci. Nat. Paris, 1818, torn. xii. p. 124. 



6 Histoire Naturelle des Animaux sans Vertebras (ed. 1), 1819, vol. vi. p. 317. 

 6 Ibid., 1836, vol vii. p. 482. 



