HYDROIDA 



41 



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

 and there. The pol\p is fusiform with the tentacles irregularly distributed all over the surface; the 

 pohp 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 

 uj^ier part of blastostyles without tentacles, at most i mm. high. 



Material: 



The P'aroe Islands: 13 miles West to South of JNIunken, depth 150 fath. (on Citrdinin sp.). 

 — — 9 — East vSouth East of Bispen, — 70 — ( - — - ). 



200 m. . 6 00 175. .■,. ...... 1000 »r7. 



Text-fig. L. Localities of Mcrona coriiucopiac • and Monobrachium parasihit, 



2000 m. 



in the Northern .\tlantic. 



Mcrona cornncopinr was first described as a Tiibiclava by Norman (1864). But as the latter 

 genus is characterized by the gonophores being borne on the polyps, 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 Tiibiclava 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. I^ut at any rate a renewed examination of tlic two genera is needed. 



Mcrona cornncopiac .seems only to occur attached to shells of living mollusk.s, and has been 

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

 very frequent; it has previon.sly been recorded from the sea to the north of the Slietlands at the 

 depth of 80--100 fathom.s, and from the coast of Northumberland. To these localities are now to be 



The Ingolf-EspiJili.m. V. i.. 6 



