NAVICELLA. 



Genus NAVICELLA, Lamarck. 

 Ti'sia oblomjo-ovata, ckpressa, Patellcpformis, interdum coii- 

 centrice striata, sapius lavigata, olivaceo-lutea vel vi- 

 rescens, nigra plerumque reticulata, spird nulla, vertice 

 ad marginem suboblique reflexo, interdum roslraio, labro 

 simplici, area columellari tettui,pland, septiformi, aper- 

 turd perampld, impressionibus musculariius duabus 

 distinctis. Operculum testaceum, mbquadratum, pla- 

 num, dente laterali aeuto. 

 Shell oblong-ovate, depressed. Patella-shaped, sometimes 

 concentrically striated, more frequently smooth, olive- 

 yellow or greenish, generally reticulated with black, 

 no spire, vertex rather obliquely inflected, sometimes 

 beaked, lip simple, columellar area thin, flat, septum- 

 like, aperture very largo, muscular impressions two, 

 distinct. Operculum testaceous, nearly square, flat, 

 with a sharp toolh at the side. 

 The Nnvicella are a group of the very characteristic 

 family of fresh-water Nerites, in wliich the shell assumes 

 a more open Limpet-like form. The spire, which in Ne- 

 rlta and Neritina is convoluted in a very simple manner, 

 and is, in some species, so concealed as scarcely to show 

 any convolution, is here transformed into the simple nu- 

 cleus of a spire with the vertex inflected, as in some of 

 the Limpets, into a beak. The callous expansion of the 

 columella, typical of this family, which is often so broadly 

 and thinly developed in Neritina, is in Navicella modified 

 into a positive septum or shelf, forming, so to speak, the 

 poop of the little boat. 



There is not much variation either of form or painting 

 in the Navicelhs. They are mostly of an olive-yellow or 

 gi-eenish colour, reticulated or blotched with black, but a 

 few are semitransparent and tinged with rose. Only five 

 species were known to Lamarck. The exploration of the 

 rivers, during the last few years, in the islands of the 

 Eastern and South-Eastern Seas have brought many 

 more species to light, and the number is increased to 

 upwards of thirty. The Navicella: are not found in Europe 

 nor in any part of the Western Hemisphere. Their chief 

 habitats are the Philippine and Australian Islands, the 

 New Hebrides, New Ireland, and New Caledonia. 



dibus reticulata, interdum nigra concent rice maculntd ; 

 intus carulescente, area columellari auratitio-tinctd. 



Janelle's Navicell.4.. Shell oblong-ovate, convexly 

 depressed, olive-yellow, reticulated with obliqut- 

 blaekish-green lines, sometimes concentrically blotch- 

 ed with black ; interior bluish, columellar area tinged 

 with orange. 



Recluz, Eevue Zool. Soc. Cuvierienne, 1841, p. 376. 



Ilab. Guam (in the river Umata) ; Janelle. Philippine 

 Islands (in mountain streams) ; Cuming. 

 A fine large oval species, reticulated or blotched with 



blackish-green upon an olive-yellow ground. 



Species 2. (Pig. a, b, Mus. Cuming.) 

 Navicella bimaculata. Nav. testd subquadrato-ovuin, 

 convexo-depressd, lutescente, lineis nigris oblique m/i- 

 culato-reticulatd ; intus carulescente, ared columellari 

 angustd, aurantio-rufo marginatd, maculis duabus ni- 

 gris notatu. 

 The ttvo-spotted Navicella. Shell somewhat squarely 

 ovate, convexly depressed, yellowish, obliquely blotch- 

 reticulated with Iilack lines ; interior bluish, colu- 

 mellar area narrow, edged with orange-red, marked 

 with two black blotches. 

 Hab. Mauritius. 



Characterized by two black blotches ou the columellar 

 area, which is rather narrov/ and tipped with orange-red. 

 and, externally, by a rather blotchy kind of network. 



Species 1. (Pig. a, b, Mus. Cuming.) 

 Navicella Janelli. Nav. testd oblongo-ovutd, convex 

 depressd, olwaceo-luted, lineis obliquis nigricaiite-vi) 



Species 3. (Fig. a, b, Mus. Cuming.) 

 Navicella depeessa. Nav. testd obovatd, depressd, sub- 

 tus subexpansd, olivaceo-luted, nigra maculato-reticu- 

 latd; intus crerulescente, ared columellari parviusculd, 

 aurantio-rufo tinctd. 

 The depressed Navicella. Shell oblong-ovate, de- 

 pressed, rather expanded beneath, olive-yellow, blotch- 

 reticulated with black; interior bluish, cohimcllar 

 area rather small, tinged with orange-red. 

 Lesson, Voy. de la Coquille, Zool. p. oCS. 



Eadem var. Navicella zebra, Lesson. 

 Hab. Tahiti. 



Distinguished by a dcpressly expanded form, which n> 

 duces the columellar area to a crescent sbn])e. 



