HYDROIDA II 



the other hand, it is perfectly correct to take the furnishment of the corbula blades with hydrothecse 

 as of primary importance, which Billard (1913 p. 85) also points out. The breadth of the single cor- 

 bula blade however, is of minor significance in this respect, and cannot be taken as proof that the 

 corbula here is more primitive than in Aglaophenia, where narrow-bladed corbulse have also been found. 



Thecocarpus myriophyllum (Linne) Nutting. 



1758 Sertularia myriophyllum, Linne, Systema naturae, ed. 10, p. 810. 



1900 Thecocarpus myriophyllum, Nutting, Plumularidse, p. 107, pi. 24, figs. 12 13. 



The colonies have an unbranched or branched, polysiphonic or monosiphonic main stem. The 

 primary tube of the stem is divided into shorter or longer internodia, each bearing about the middle 

 a short apophyse, directed obliquely forward and sideways; at the base of this at its upper side there 

 is a pair of sarcothecas, and on the basal part of the internodium an unpaired median sarcotheca. The 

 short internodia of the hydrocladium have each a large hydrotheca, slightly compressed laterally, and 

 three sarcothecse, a supra-calycine pair at the hydrotheca opening and a short proximal unpaired sar- 

 cotheca, the opening margin of which does not reach up to the middle of the hydrotheca; all sarco- 

 thecae are adcaulinally split. The hydrotheca margin is furnished with a strong, sharply cut median 

 abcauline tooth; between this and the hydrocladium the margin is slightly dentate or curved, more 

 faintly near the hydrocladium than farther from it. The opening margin stands almost perpendicular 

 to the hydrocladium. 



The gonothecse proceed from a hydrocladium which is transformed into a narrow-bladed cor- 

 bula having its blades (ribs) furnished with a basal hydrotheca, and in addition, on the outer side, 

 numerous sarcothecae. Between the corbula and the stem the hydrocladium has a varying number of 

 hydrothecse. The gonotheca is pear-shaped. 



Material : . 



"Ingolf" St. 15 66i8' N., 2559' W., depth 330 fathoms -f- 0,75 



35 6 5 i6' N, 55 o 5 ' W., 362 3,6 



- 81 6i44' N., 27oo' W., 485 6,1 



"Thor" 63 1 8' N., 21 "30' W., depth 178 metres 



6ii 5 ' N, 9 35' W, 872 



Iceland: 3 miles E. of Bjarnaroi, 70 fathoms. 



Thecocarpus myriophyllum is undoubtedly the most frequently occurring Aglaopheniid in the 

 eastern part of the North Atlantic (fig. L). It is therefore highly peculiar that it should now have 

 been met with for the first time by the "Ingolf in Davis Strait, where no specimen had previously 

 been found. In Iceland waters also, reliable data have hitherto been extremely rare, though Sse- 

 mundsson (1911 p. 105) records the species from the south-west point of Iceland, albeit under the 

 name of Thecocarpus radicellatus. We can now add the further finds in these waters from Danmark 

 Strait and east coast of Iceland. Thecocarpus rnyriophyllum is a species belonging to the lower littoral 



