UMBRACULID^K. 175 



free margins of which have a row, in part doubled, of short, strong, 

 irregular denticles. 



Mauritius, in stomach of the nudibraneh Trevelyana croeea. 



Ildica nana BGH., Malac. Unters., ii, Auhang, p. 870, pi. 82, f. 

 27-38. 



Two individuals with part of another were found in the stomach 

 of a nudibraneh. 



PI. 69, figs. 52, 53, animal enlarged, view of the right side and 

 above ; fig. 50, shells ; fig. 55, lateral tooth, from above ; fig. 54, two 

 rows of teeth, showing the lunate centrals in the middle, laterals 

 on each side ; fig. 57, stomach plates. 



Family UMBRACULIDM 



= Umbrellidce Auct. 



Shell external, limpet-like, with the nucleus minute and sinistral, 

 vertex near the center ; inside with a circular, closed muscle-impres- 

 sion. 



Foot oval or oblong, adapted for creeping, without pleuropodial 

 processes. Head bearing two laterally-slit tentacles, the eyes sessile 

 at their inner-anterior bases. Mantle the size and shape of the shell, 

 with thin, serrate edge. Gill a long plume lying between mantle 

 and foot on the anterior and right side, adnate and bearing numer- 

 ous bipinnate branches for the greater part of its length, posterior 

 end free and bipinnate. Anus tubular, projecting behind the gill. 

 Mouth with labial tentacular or plate-like processes; radula very 

 broad, bearing a great number of similar, very narrow, crowded, 

 needle-like teeth, with recurved simple cusps, which are not differ- 

 entiated from the body of tooth. 



Distribution, world wide in tropical and subtropical seas, lamina- 

 rian zone and deeper. 



This very distinct family is composed of two genera, strongly 

 divergent in the relations of the male genitalia and gill. 



Genus UMBRACULUM Schumacher, 1817. 



Foot very fleshy, large, oval, with a deep anterior sinus in which 

 the mouth-parts are situated. Gill a long adnate plume, extending 

 across the front and along the right side, free and bipinnate behind. 

 Penis external, lying in the anterior sinus of the foot, in the median 

 line in front of and below the head. Shell depressed, entirely calci- 

 fied, with the vertex to the left of the middle. 



