Onchidella.} GASTROPODA. 809 



Genus 1. ONCHIDELLA, Gray, 1850. 

 Oncidiella, Crosse and Fischer. 



Body oval, mantle thick, its upper surface warty, cariuated at the 

 periphery, which is irregularly notched, often with short radial riblets ; 

 it contains large multicellular glands opening at the tips of the larger 

 lobes. There are no dorsal branchiae nor dorsal eyes. Hyponota in 

 width equal to the sole or reduced to one-third of it ; they have on 

 each side a slender fold, parallel to the margin of the sole, the hyponotal 

 line, which extends from the ommatophores to the pneumostome ; this 

 fold is wanting in other genera of the family. The female genital 

 furrow is extended posteriorly beyond the female genital orifice, and 

 its folds are united with the circular wall of the anus. Male genital 

 orifice outside and a little behind the right ommatophore. Recep- 

 taculum serninis with a long neck ; vas deferens short. Male organ 

 tender, without an accessory gland, mostly with calcareous concre- 

 tions in its lumen. Lung-cavity and kidney symmetrical. Chylific 

 stomach very small. Jaw thin, striated. Radula with the central 

 tooth tricuspid, the lateral teeth with an elongated broadly rounded 

 inner cusp and a sharp small outer denticle. 



Distribution. All seas. 



The animals live in the littoral zone, hiding in crevices of rocks 

 during high water. They feed on algse, and they are amphibious. 

 They are able to remain under water for one month without any 

 inconvenience, and, on the other hand, they can remain for the same 

 length of time exposed to the air if there is sufficient moisture in it. 

 The pneumostome is closed in the water, but opened in the air. 



KEY TO SPECIES. 



A. Notum black, sometimes variegated with white. 



a. Notum smooth, with small white spots ; 19 marginal glands ; 



hyponota in width one-half to three-quarters of sole . . obscura. 

 aa. Notum granular, with some larger papillae. 



b. Back convex ; 28-32 marginal glands ; hyponota in width 



one-half of sole . . . . Campbelli. 



bl>. Back sharply rounded ; 16-20 marginal glands ; with ' 

 width of hyponota equal to that of the sole. Appendi- 

 cular gland very large ; receptaculum seminis distal. . nigricans. 



B. Notum yellowish -white with brown spots and distant unequal 



round papilla? ; 19-24 marginal glands ; hyponota of the same 



width as the sole . . " flavescen*. 



C. Notum yellowish-green to brown, with patches of dark grey, 



granular, with larger papillae ; 19-20 marginal glands ; hypo- ( te n oides _ 

 nota the same width as the sole . . - { rrora t a 



1. Onchidella Campbelli, Filhol, 1880. Plate 32, figs. 1, a. 



Onchidella Campbelli, Filhol, " Comptes Rendus," xci, 1880, 1094 ; Miss. 

 I.C., 1885, 521 ; Index, 58. 



Animal elongated oval, back convex, not keeled, warty, with 

 numerous marginal glands. Tentacles short, rounded at their tips. 



