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



was soon followed up by my research on Marsenina prodita? Subsequently H. v. Jhering 2 

 contributed an investigation of the nervous system of Marsenina perspicua, and G. 0. 

 Sars 3 finally published a research on the oral parts of Marsenia latens, Marsenina prodita, 

 and Onchidiopsis glacialis. By several naturalists, especially Dall and Verrill, some new, 

 but more or less doubtful, species have been added. 



Even the Challenger expedition has made but scanty contributions to the group ; it 

 has however brought to light a generic form of great interest. 



Family Maeseniadje (Leach), Bergh. 



Marsenia, Leach, 1820, Moll. Brit. Synopsis (ed. Gray), 1852, p. 26. 



Lamellariacea, Loven, Ofvers. Vet. Akad. Handl., 1847, p. 192. 



Lamellaridce, Gray, Figures of Moll. Anim., 1850, vol. iv. p. 75. 

 I Lamellariadce, Gray, Guide, 1857, vol. i. pp. 27, 28. 

 ( Velutinidce, Gray, p.p. (Joe. cit.), 1857, p. 46. 



Marseniadai, Bergh, Monogr. (loc. cit.), pp. 243-359, tab. i.-v. 

 ( Marseniadce, Troschel, Das Gehiss der Schnecken, vol. i., 1856-1863, pp. 185-188, pi. xvi. figs. 1-5. 

 \ Velutinidce, Troschel, p.p. (loc. cit), pp. 167-169, pi. xv. figs. 17-19. 



Mollusca gastrceopoda prosobranchiata {strepioneura, azygobranchiata). 



Pallium ampliatum, incrassatum, supra laeve vel nodulosum vel grosse tuberculatum ; 

 vel continuum, testam recondens, vel culmine fissum, testam pro parte detegens. Limbus 

 pallii vel amplus et planus, vel crassior et rotundatus, ultra margines podarii productus ; 

 pro siphone antice in pagina inferiore limbi semicanali exaratus cum plica marginali vel 

 emarginatura ; in medio lateris dextri limbi interdum semicanalis et plica similis. 



Testa semper adest, ut plurimum obtecta, interdum partim denudata ; — turn spiraliter 

 convoluta, paucigyra, calcarea, tenuis, semper absque margarita ; apertura ampla, margine 

 columellari simplici arcuato, antice vix cum fiexuras vel emarginatura? vestigio; — turn 

 cornina, scutiformis, absque spira. 



Cavitas brancliialis duabus branchiis instructa ; altera spuria, antica, minore, foliolis 

 homomallis ; altera vera, postica, majore, foliolis secundis. 



Caput depressum, antice truncatum. Tentacula quasi ex angulis capitis orta, teretia, 

 basi depressa, vel subcylindrica vel subconica ; oculi in tentaculorum basi externa sessiles, 

 quasi ophthalmophoriis brevibus inserti. 



Rostrum retractile, sat longum, validum, per rimam oralem inferiorem transversalem 

 (os externum) exsertile ; os internum utrinque lamina mandibulari cornina validiori 



1 E. Bergh, Bidrag til en anat. Unders. af Marsenina prodita (Loven), Vid. Meddel. nat. Foren. 

 Kjvbenhavn, 1857, pp. 110-122, tab. i. 



2 H. v. Jhering, Vergl. Anat. des Nervensyst. u. Phylogenie d. Mollusken, 1877, pp. 115-117. 



3 G. 0. Sars, Moll. reg. arct. Norv. 1878, pp. 150-153. 



