96 HYDROIDA II 



Gen. Sertularella Gray. 



Upright colonies with sympodial growth. The opening of the hydrotheea is furnished with 

 three or four marginal teeth, between which are attached as many triangular opercular plates closing in a 

 pyramid over the aperture. 



The definition here agrees with that given by Levinsen (1913 P- 30). The genus seems, how- 

 ever, to form a somewhat heterogeneous collection of species which should, probably, from the struct- 

 ure of the polyp, be divided into two groups or genera. Of these groups, Sertularella sens str. will 

 then comprise species with abcauline blind sack, while in the other group, we have species where 

 this is rudimentary or indiscernible on external observation. The latter group leads, as above menti- 

 oned, to Diphasia and Dynamena, while the former gives the point of origin for the remaining genera 

 of Sertulariidce. The most primitive group is that of the species without visible blind sack. 



Sertularella tamarisca (Linne) Levinsen. 

 1758 Sertularia tamarisca, Linne, Systema naturae, ed. 10, p. 808. 

 1893 Sertularella tamarisca, Levinsen. Meduser, Ctenophorer og Hydroider, p. 58. 



Upright, somewhat irregularly branched, as a rule pinnate colonies, without distinct main stem. 

 The hydrothecee, which have a tripartite lid and tridentate opening margin, are set in two rows along 

 the branches, a pair of hydrothecse oppositely placed on each interuodium. The hydrothecee are very 

 large, almost cylindrical, with the distal half free and highly diverging from the branch. 



The male gonotheeee are reversed conical, compressed distally with a small tooth on either side 

 and a short cylindrical neck centrally placed. The females are of the same shape, but have three 

 distal broad blades, each furnished with a longitudinal indented median ridge; the three blades close 

 in tu a pyramid and form a large external marsupium, in which the larvee are developed. 



Material : 



"Iugolf" vSt. 11, 64°34' N., 3i°i2' W., depth 1300 fathoms, t,6 



- 87, 6 5 °o 2 ,3' N, 23^56,2' W., - 



- 95, 65" 1 4' N, 30*39' W., 



- 98, 6 5 ° 3 8' N, 26*27' W., 



- 144, 6 2 °49' N., 7°i2' W., 

 "Thor" 63°3o' N., 20°i4' W., 

 Iceland: 6 miles W. of Isafjord, depth 55 fathoms 



5 — E. of Seydisfjord, — 135 

 6 3 °2i' N, I7°i 5 ' W., 58 



The Faroe Islands: 16 miles S. by E. of south point of Nolso, depth 80 fathoms. 



Sertularella tamarisca presents, as a matter of fact, a somewhat alien impression among the 

 remaining Sertularella species, and has led an unsettled existence, now in this genus, now in Diphasia 

 or Dynamena. The paired arrangement of the hydrotheea; and the remarkable female gonotheea- of 



