52 



i" that the genus Dcsjiioptcrus belongs to the Thecosomata. 

 2" that it must be referred to the Cymbuhidae. 



Besides, I am of opinion that the specimen of Ciu'N and that of the Siboga Expedition 

 are nothing but young stages of other species. This supposition is based on the following facts: 

 i" in the twisting of the liver into a spiral at the posterior end of the visceral mass; this 



twisting proves, that the animal has scarcely surpassed the embryonic stage, in which a 



calcareous external shell is present ^). 

 2" In the position of the anus at the right side ^). 



Furthermore may be remarked, in favour of this o])inion: 

 i" that a gonad is properly not present, as the polygonal ova, situated at the dorsal side ot 



the stomach, are not joined by any connective tissue. 

 2° that any trace of a penis is absolutely wanting, 

 3" that the animal is very small; the greatest width across the fins is 3,5 mm. 



The crenus Gleba was founded by ForskIl ") on an animal which most zoologists after 

 him called Tiedemaiinia ^) ; these names being quite synonymous, the first of those must 

 be retained. 



So the three following titles remain : 



(i) Cymbulia. (2) Cymbtdiopsis. (3) Gleba. 



It is very difficult to obtain absolute certainty as to the specific distinctness of many 

 forms, referred to the Cymbuliidae. This is due to the fact, that most species have been described 

 and figured by its discoverers in a way so vague and incomplete, that it is almost impossible to 

 recognize the type on which the species has been based. Pelseneer is the only one who has tried ■*) 

 to give short and clear diagnoses of all the forms, then known. Taking into consideration the 

 literature on this subject and the material at my disposal, I propose the following diagnoses : 



1 . Cymbulia : proboscis short, and fixed to the fin ; fins with a ventral lobe, ending in a whip- 

 like process; on the dorso-lateral margin the fins exhibit an area devoid of muscular fibres"); 

 muscular bundles are distinctly radiating towards the lateral and ventral margins of the fins, 

 and in the ventral lobe. — Shell very thick, especially at the dorsal extremity, in which 

 the cavity extends ; slipper-like ; covered with spines, which are arranged in rows parallel to 

 the dorso-ventral axis. 



2. Cymbtiliopsis : proboscis projecting, free; fins with a continuous margin, without ventral lobe, 

 on the surface of the fins three sets of muscles may be distinctly seen ; the visceral nucleus 

 is rounded at its aboral extremity, where it exhibits a dark jiigmented ring or a spot. — 

 Shell ovoid ; with a large cavity and a broad aperture, about as long as the half-length of 

 the shell ; it is covered with rounded tubercles. 



i) See Kkohn, BeitiSge z. EnUv.-Gesch. dor Pterop. u. Heterop. Leipzig iS6o. 



2) Icones rerum natuvalium, pi. XLIII, fig. D. 



3) Erected by Delle Chi.\ie, in van Beneden, Exeicices zootomiqucs. \ouv. Mem. .\cad. Bru.x., vol. XII, p. 22. 



4) •>•<;. 93, 96. 



5) This area has been indicated in the figure of Boas (Spolia .itlantica, pi. 3, fig. 30) as a deep notch in the fin margin, while 

 in reality there is only a slight sinuosity. 



