542 GASTROPODA. [Opisthobranchia, 



rapidly increasing, the last truncated above, rounded at the base, 

 narrowed and flatly convex above. Aperture elongated oval, slightly 

 excavated above by the parietal wall, broad and open toward the base. 

 Outer Up thin, sharp, almost straight for the upper two-thirds, then 

 forming a regular arch with the convex basal Up. Inner lip forming a 

 rather broad but very thin callosity upon the parietal wall, incon- 

 spicuous on the columella, which descends with a rather sharp margin, 

 but slightly excavated, to the basal lip. Umbilicus patulous, distinct. 



Diameter. 2-3 mm. ; height. 3-5 mm. 



Animal unknown. 



Type in the Dominion Museum, Wellington. 



Hab. Off Great Barrier Island, in 110 fathoms. 



Remark. The species is distinguished by the almost total absence 

 of spiral sculpture and the presence of a distinct umbilicus, which is 

 an exception in this genus. 



Fain. AGLAJID^, Pilsbry. 

 Doridiidce, Fischer and of authors. 



Animal bearing 2 dorsal shields, with a furrow between them. 

 The anterior shield has free margins, but as a rule is not developed 

 into tentacles ; the posterior has the margins less developed, but is 

 produced behind into two processes. The foot is broad, truncate 

 before and behind, and continued on each side into a fairly ample 

 parapodium. from which it is not clearly divided. The parapodia 

 are divided behind, and the posterior part of the body hangs over or 

 rests on them. Organs analogous to rhinophores are often present in 

 the form of lamellfe under the sides of the head-shield or lumps with 

 bristles around the mouth. The branchia is a large bipinnate plume, 

 posterior and on the right side. Behind it is the vent, in front of it 

 the genital orifice, which is connected by an open groove with the verge 

 on the right anterior extremity of the body. The verge is grooved, the 

 prostate double or single. 



The shell is wholly internal, posterior, and generally composed of a 

 minute spire with a single solute whorl ; sometimes wholly membranous, 

 sometimes partly calcined, rarely wholly calcified. There are no jaws, 

 radula, or stomach-plates, but there is, as a rule, a large, sometimes 

 colossal, buccal bulb with thick muscular walls. (Eliot.) 



Genus 1. AGLAJA, Renier, 1807. 



Aglaja, Renier, Tav. di Classificazione, 1807, 8. Type : A. tricoloruta, 

 Renier. Doridiwm, Meckel, 1809. Acera, Cuvier, 1810. EidotJu-a, Risso, 

 1826. Melanochlamys, Cheeseinan, 1881. Posterobranchcea, d'Orbigny, 

 1837? Bullidium, Leue, 1813. Lobaria, Blainville, 1825. ? 1'Jiilinopsis, 

 Pease, 1860. 



Characters. Those of the family, but the head-shield without 

 rhinophores or frontal processes. 



