i6o 



ACTINIAR1A 



verrucae + = v. present, d +, d:o = reproductive organs on the directives present resp. absent. 



Gentis Urticina Ehr. 



Diagnosis: Cribrinidae with well developed pedal disc and rather low body. Column with verrucae 

 or without. Acrorhagi and pseudoacrorhagi absent. Sphincter strong, palmate or pinnate. Tentacles simple, 

 thick, cylindrical, short. Longitudinal muscles of the tentacles from ectodermal to ecto-mesogloeal (meso- 

 gloeal?). Radial muscles of the oral disc from ectodermal to meso-ectodermal. Numerous perfect mesenteries 

 decamerously (during the development hexamerously) arranged. Well developed mesenterial muscles. The 

 six primary pairs of mesenteries always sterile. The 10 or the 20 strongest pairs mostly without reproductive 

 organs. Nematocysts in the ectoderm of the tentacles and in that of the actinopharynx of very different size. 



As before pointed out, it is very difficult to distinguish Urticina from some other genera, especially 

 if the reproductive organs are lacking. The specimens provided with verrucae have certainly been confounded 

 with specimens of Cribrinopsis, sometimes also with certain species of Cribrina, and the smooth forms with 

 Epiactis- and Leiolealia-species. To him who has more closely examined the Northern species of these genera, 



