HYDROIDA II j-c 



is attached. The hydraiitli lias a proximal tentacle crown, the growth of which takes place from the 

 part of the hydranth periphery nearest the stalk, where the shortest tentacles are found. The tentacles 

 of the oral circle are homogeneousl\- developed. The i)criderm of the stalk is reduced and soft. The 

 blastostyles are situate between the tentacle crown.s, the youngest ventrally above the point of at- 

 tachment of the stalk. The pohps are solitary. 



Allman (1888 p. 5) described the first Branchiocerinnthus species, which was brought home 

 by the "Challenger", under the name of Monocaiilus uiiprnilor. The family Monocaulidce had been 

 previously founded by A 11 man n (1871 p. 395) with the following diagno.sis: "Hydrocaulus solitary, naked. 

 Hydranths with a prt)ximal and a distal set of filiform tentacles. — Gonophores in the form of fixed 

 sporosacs". This diagnosis thus makes no mention of the essential point, to wit, the bilateral character 

 of the polyp. Nor is any reference to this found under the heading of the only genu.s, Aloiiocait- 

 lus, which is thus described: 



"H^■drauth abruptly distinct from the hydrocaulus; i^roxinuxl tentacles longer than tlie distal 

 and disposed in a single verticil near the base of the hydranth, the distal set scattered o\er a zone 

 close to the summit of the Indranth. — ,S]5orosacs borne upon peduncles, which spring from the body 

 of the hydranth between the proximal and distal sets of tentacles. 



The genus A/ofiocdiilus is constituted for the Coryuiorpha glacialis of Sars, a form which, 

 though its trophosome is that of a Coryiiiorplia^ is yet strongl)' distinguished from the true Corymor- 

 phas by its adelocodonic gonophores" (Allman 1871, p. 396). 



In addition to Coryinorplia glacia/is, Allman also places Coryuiorpha pnidiila L. Agassiz in 

 the genus, this being a species with free medus;e. I^ater on, Coryuiorpha grocnlandica is also placed 

 in tlie same genus. And here, finally, Monocajilus iniprrator is likewise included, Allman (1888 p. 5) 

 having entirely overlooked the bilateral structure of the species, and disregarding tlie morphological 

 peculiarities noted in his descriptions. 



With reference to Coryniorplia I have pointed out that All man's tyjjical Afoiiocaulus, Cory- 

 viorphd glacialis M. Sars must remain in the genus where M. vSars placed it, like MoHocnulns groen- 

 huidica Allman, the onh' species which entirely answers to the diagnosis given by Allman. It would 

 therefore be altogether wrong to follow the suggestion gi\en in "Xomina conservanda" (cf. p. 53) and 

 retain the generic name Afoiiocaitl/is for a genus where Moiwcaiiliis iniprrator has been somewliat 

 arbitrarily chosen as type, the more so since the essential feature of the species, which is even cha- 

 racteristic of the genus as a family type, was distinctly emphasised by E. L. Mark in 1899 in his 

 description of the central American Pacific species Brauchioccriaiifhus urcrolus Mark. Since then, the 

 genus has been referred to in all leading works under the generic name given it by Mark, Bra 11- 

 chioceriajithus^ and as the species in cjuestion have been accorded onl\- the briefest mention in the 

 handbooks, there will be no confusion caused by general adoption of the appellation. Moreover, after 

 the publication of the fundamental studies on Braiichioccriaiithns by Mark (1S99), Miyajima (1900), 

 and Stechow (1908, 1909) it would certainly be confusing to adopt the name Monocaulus. 



The genus Brauchiocerianthns was hitherto only known from the Pacific (Alaska, Japan, Pa- 

 nama) and the Indian Ocean (Belucliistan, Oman, and East Africa). Stechow, in his description of 



