110 THE VOYAGE OF H.M.S. CHALLENGER. 



often one of its free ventral margins overlaps the other ; the superior half is comparable 

 to the cowl of the mantle, and includes the simple ovate ascending phollocyst. The free 

 inferior part of the mantle-lobes often exhibits two small prominent teeth. 



The genus Cucullus was founded by Quoy and Gaimard upon an Australian Eudoxia, 

 which they figured first under the name Diphyes cucullus (2, p. 92), synonymous with 

 Eudoxia lessonii of Eschscholtz (1, p. 126). Blainville called the former in 1834 

 Cucullus doreyanus (24, p. 131), and Lesson himself separated the latter as Cucullus 

 lessonii (3, p. 459). Indeed the genus Cucullus of the French authors (published 

 in 1834) is identical with Eudoxia of Eschscholtz (1829). But since Gegenbaur 

 and Leuckart, in 1853, demonstrated that the Eudoxia^ are the isolated cormidia of 

 Diphyidse, the term Eudoxia is generally used for all these " Diphyozooids " (Huxley, 

 1859, 9, p. 57). It seems, therefore, . best, to avoid further confusion — to employ the 

 term Cucullus for the monogastric generation of those Diphyidse which constitute the 

 genus Diphyes in the strictest sense (compare below, Genus 27). The typical and 

 oldest species remains Cucullus lessoni, as the free Eudoxia of the Pacific Diphyes 

 i ippendiculata, Esch. 



Scarcely different from Cucullus is the genus Cucubalus of Quoy and Gaimard. 

 This genus, however, may be retained for the Eudoxise of the Monophyid Muggisea, which 

 are very similar to those of Diphyes. (Compare the preceding genus.) 



Many bottles of surface animals in the Challenger collection contained specimens of 

 Eudoxise belonging to Cucullus, and in some cases it was possible to demonstrate their 

 connection with a species of Diphyes contained in the same bottle as the former. 

 Supported by the comparative study of these forms, and of similar forms compared in 

 other collections, and partly observed living by myself, I have been led to state the 

 ontogenetic connection of the following species of monogastric Cucullus with corre- 

 sponding species of polygastric Diphyes : — 



1. Cucullus lessoni, Lesson (3, p. 459), synonymous with Eudoxia lessonii, 



Eschscholtz (1, p. 126), is the free Eudoxia of Diphyes appendiculata, 

 Esch. (1, p. 138), taken in the Pacific. 



2. Cucidlus gracilis, Hkl., synonymous with Eudoxia bojqni, Esch. (1, p. 125) 



and Huxley (9, p. 59), is the free Eudoxia of Diphyes gracilis, Hkl., 

 taken in the Southern Pacific and in the Indian Ocean. 



3. Cucullus elongatus, Hkl., is the free Eudoxia of Diphyes elongata, Hyndman 



(64, p. 166), occurring in different parts of the Northern Atlantic, Gulf 

 Stream, &c. 



4. Cucidlus gegenbauri, Hkl., synonymous with Eudoxia messanensis, Ggbr. 



(7, Taf. xvi. fig. 4), is the free Eudoxia of Diphyes sicboldii, Koll. 

 (4, Taf. xi.), Mediterranean and Tropical Atlantic. 



