ACTINIARIA 

 174 



Urticina felina crassicornis X Cribrinopsis (or Cribrina)? 



Dimensions in strongly contracted state: height 2,2 cm, largest breadth 5 cm. 



Occurrence: Greenland without distinct locality, i sp. 



In a bottle, containing, among others, Urticina felina crassicornis and Cribrinopsis similis, I found a 

 specimen, which I must for the present consider as a hybrid between these two nearly allied genera, or pos- 

 sibly between Urticina and Cribrina. In most characters it agrees with Urticina felina crassicornis. The 

 colunm was devoid of sucking warts. The nematocysts in the ectoderm of the tentacles were 25 — 31 x (2) 

 2,5 fjt, in the actinophar>'nx 58 — 67 X 5 /i. The spirocysts of the tentacles variated from 22 X i — 1,5 // to 

 48 X 2,5 fi. The longitudinal muscles of the tentacles and the radial muscles of the oral disc were of the same 

 appearance as in Urticina. The sphincter was palmate (without a distinct main lamella). The pairs of me- 

 senteries were 10 + 10 + 16 = 36. Among the pairs of the last cycle two on each side of the directive plane 

 were not developed. On one side the pairs i and 9 were wanting, on the other the pairs 8 and 9. In the lower 

 part of the actinopharynx 10 pairs were perfect, more distally 20 pairs ; the mesenteries of the last cycle 

 almost reached the actinopharynx. In the coelenteric cavity there were numerous embryos. The mesenteries 

 contained numerous small eggs and such were present also on the mesenteries of the first and second cycles, 

 which I have verified also on sections. The distribution of the reproductive organs thus agrees with that 

 in Cribrinopsis and Cribrina, but not with that in Urticina. In this last genus the first 10, or in very large 

 specimens the 20 oldest pairs namely commonly are sterile; in small specimens of U. felina coriacca I have 

 found only the six first pairs to be without reproductive organs (compare Urticina felina coriacca). As the 

 specimen was comparatively large, I think that it is difficult to consider it as a pure Urticina. An Urticina 

 of the same size as our specimen has namely at least the 10 first pairs of mesenteries sterile. It is true that 

 in certain genera, as in Urticina, a displacement in the appearance of the reproductive organs takes place, so 

 that with the increasing age of the animal a cycle of mesenteries, which was fertile in young individuals, 

 becomes sterile in older ones, in other words, the reproductive organs appear in older individuals in a later cycle 

 than in younger ones, but I have never observed that a species beginning by developing the reproductive 

 organs on the mesenteries of the first cycle afterwards loses this capacity, so that in a later reproductive period 

 the fertility appears first on the mesenteries of the second cycle. I also think that a hybridisation between 

 Urticina and Cribrina or Cribinopsis may be admitted, as the species occur together (compare p. 156). 



Genus Epiactis Verr. 



Diagnosis: Cribrinidae with smooth column, without warts, acrorhagi and pseudoacrorhagi. Column 

 with (or without?) a cuticle. Tentacles simple, cylindrical or conical, short. Longitudinal muscles of the ten- 

 tacles and radial muscles of the oral disc ectodermal. Mesenteries hexamerously arranged (always?). Repro- 

 ductive organs found on the mesenteries of the first cycle and on the other stronger mesenteries. 



The diagnosis given by Stephenson (i9i8ap.24) of the genus is too comprehensive, as, according to 

 that formation, the genus Isotealia, as well as Urticina felina crassicornis, and possibly certain specimens of 

 Cribrinopsis similis, may be arranged into the genus. Therefore I have set up a new, somewhat more distinct 

 diagnosis, by which also the genus Pseudophellia Verr. may be included (compare p. 145 — 146). Concerning 



