HYDROIDA 



41 



extended polyp; they are without rings; at most there is some faint and irregular wrinkling here 

 and tiiere. The polyp is fusiform with the tentacles irregularly distributed all over the surface; the 

 polyp may be retracted into the broader distal portion of the hydrocaulus. 



The structure of the gonophores seems to be strongly reduced. They are developed at the 

 upper part of blastostyles without tentacles, at most i mm. high. 



Material: 



The Faroe Islands: 13 miles West to vSouth of Mnnken, depth 150 fath. (on Oirdiiun sp.). 

 — — 9 — East South East of Bi.spen, — yo — ( - — - ). 



zoom. . 600/71. .^ tooom. 2000m. 



Text-fig. L. Localities oi\Utrona cormccopiac % and Monobrachium parasitum ▲ in tlie Northern Atlantic. 



Mcrona cornucopiac was first described as a Tnbiclava by Norman (186^). I?ut as the latter 

 genus is characterized by the gonophores being borne on the polyp.s, he thought he had better set 

 up a new genus Mcrona (1865) for the species in hand, bearing its gonophores on polyps strongly 

 reduced or on blastostyles. This criterion, however, is of subordinate importance and would by no 

 means justify the separation of two genera. However, from the drawings occurring in literature, a 

 much essential point of difference urges itself. The perisarc of the species of Tnbiclava is not so wide 

 that the polyp can be retracted into it, while this is the case with Mcrona. The division, therefore, 

 seems well founded. But at any rate a renewed examination of the two genera is needed. 



Mcrona cormicopiac seems only to occur attached to shells of living mollusks, and has been 



found on species of the genera Cardiuni, Astartc. and Dcntalhtin. The species does not seem to be 



very frequent; it has previously been recorded from the sea to the north of the Shetlands at the 



depth of 80-100 fathoms, and from the coast of Northumberland. To these locahties are now to be 



6 



The Ingolf-Exptdition. V. 6. 



