Only one genus is known. 



Notobranchaea Pelseneer. 



1825. ? Clio (part.) Rang, Description d'un nouveau genre des Ptcropodes et dc deux cspeces 

 nouvelles du genre Clio, Ann. d. Sc. Nat., ser. I, vol. V, p. 286. 



1863. Clio (part.) Macdonald, On the Zoological Characters of the living Clio caudata, Trans. 

 Roy. Soc. Edinb., vol. XXIII, p. 1S6. 



1886. Notobranchaea Pelseneer, Description d'un nouveau genre de Pteropode Gymnosome, 



Bullet. Sci. Dep. Nord, p. 224. 



This genus was established by Pelseneer, but the little material at his disposal did not 

 enable him to give a complete diagnosis. 



The characters of this genus are the following, according to my own researches : 



Buccal cones: two pair of short cephaloconi, disposed in the same manner as in 

 Cliotie, viz. inserted on the wall of the buccal cavity, at the outside of the ''false lips", w-hile 

 a hood circumscribes an opening, corresponding vi^ith the true buccal aperture in the Pneumono- 

 dermatidae and Clionopsidae. Pelseneer ascribes to Nofodraiickaca only one pair of cephaloconi, 

 but I have seen two pair of them in the same species that was studied by him. In this respect 

 Macdonald is right whose description, for the rest, is too obscure and too short as to 

 recognize with certainty the species to which his "trigonal tailed Clio'' belongs. 



Posterior gill: the fringed dorsal crest is a very complicated winding fold of the 

 skin. I have seen a larva (most probably belonging to the same genus) in which the three 

 crests consist of a great many dermal glands closely grouped together, and in which a gill 

 properly so called is not present. I shall refer to this larva again. 



Radula : without median tooth, quite the same as has been described above for the family. 



Hook-sacs: short, with a few hooks. 



The famih' of the Notobranchaeidae shows very great resemblance with the Clionidae, 

 and it may be expected that when more species will be discovered, these two groups will have 

 to be united to a single family. 



Of the two species hitherto described, one was found by the Siboga. 



I. Notobranchaea inopinata Pelseneer. (PI. V, figs. 129 — 135). 



1887. Notobranchaea inopinata Pelseneer, Chall. Rep., LVIII, p. 40, pi. Ill, figs. 5 — 6. 

 Stat. 144. Damar Island. 3 spec. 



, Body: ovate, posterior extremity much contracted in the pre:;erved specimens. Head 

 broad, bilobated, distinctly separated fn^n the neck. Pigment in one specimen chiefly distributed 

 on the right side; in the two other specimens it is entirely absent. 



P^oot: the anterior lobes (fig. 133) are rather broad, free in their posterior half. The 

 tubercle is rounded. Posterior lobe short, but pointed with a longitudinal ridge. 



Posterior gill: consisting of a much wound fold, without real fringes (fig. 134). 



