BOWERBANKIA IMBBICATA. 519 



same genus. They all possess eight tentacles ; they are 

 of slighter build and more delicate habit than B. imbri- 

 cata, and the structural features are less strongly pro- 

 nounced than in the latter^ but there are no differences 

 between them of generic value. They are all furnished 

 with the manducatory organ_, and have the arms ar- 

 ranged in a perfect circle. 



Little is known as yet of the distribution of the Cteno- 

 stomata generally. The forms have been so imperfectly 

 discriminated that some doubt necessarily attaches to the 

 identification of the species, and at the same time the 

 comparative difficulty of preserving them has greatly 

 limited our knowledge of the foreign members of the 

 group. 



The genus Bowerbankia has one representative at least 

 on the northern coasts of America {B. gracilis, Leidy); it 

 has occurred in the Caspian Sea ; and I have detected spe- 

 cimens of B. imbricata form densa on an Alcyonidium from 

 the White Sea_, for which I am indebted to M. Meresch- 

 kowsky. Smitt records it from Norway and Spitzbergen. 



Valkeria Vidovici of Heller, from the Adriatic, is also 

 probably referable to this genus ^. 



BOW^ERBANKIA IMBRICATA, AdamS. 



Plate LXXIII. figs. 1, 2. 



Sertularia imbricata, Adams, Linn. Trans, v. 11, pi. ii. figs. 5-11 : J. V. 



Tkomjjs. Zool. Illust. 94, pi. i. figs. 1-4. 

 Valkeria glomekata, Coldstream, Ediub. N. P. Journ. ix. 235, pi. ii. 



figs. 1, 2. 

 Seiiialaria imbricata et verticillata, Tem^leton, Mag. Nat. Hist. is. 4G7, 



fig. 66. 

 Valkeria imbricata, Johjist. B. Z. ed. i. 254 : ? Couch, Com. Faun. iii. 95, 



pi. xrii. fig. 2. 



* Kirclienpauer mentions a Vesicularian, apparently allied to B. pustu- 

 losa, which had been brought by Dr. v. Martens from Yokohama. 



