34 Mr. G. Busk on Polyzoa collected on the Coast 



^, , Suborder II. Cyclostomata. 



IV Pam. iDMONEADiEj Busk {English Cyclopedia, Art.*^ Polyzoa^'). 



-nmau xUfw ^. // 'iil - OH, .„ 



;;jrfor;n^i?n "^o 1>ic"? ^yillv Idmonea, Lamx. 



1. /. atlantica, Ed. Forbes. PL I. fig. 6. 



Y^^, atlantica, Johnst. Brit. Zooph. 2nd edit. vol. i. p. 278. pi. 48. 

 7. radians. Van Beneden, Bull, de I'Acad. de Bru^lLes, t. xvi. 

 p. 647. pi. 1. figs. 4-6. finiBis 



In external habit /. atlantica very closely approaches some 

 forms of the Australian 7. radians, Lamk., figured and described 

 by M.-Edwards (Sur les Crisies, &c., p. 25. pi. 12. figs. 4, 4 flf 

 & 4 6), but the figure has been taken from an imperfectly 

 grown specimen. In all essential characters, however, the two 

 forms are perfectly distinct. In 7. radians the mouth of the 

 tubes is distinctly bilabiate, in 7. atlantica simple or merely 

 sinuated ; in 7. radians the surface of the branches is perforated 

 like a sieve with numerous closely contiguous pores, whilst in 

 7. atlantica it is quite smooth and merely dotted with minute 

 white spots. The branches also in 7. atlantica are not nearly, 

 so much compressed as they are in 7. radiatis, in which, as in, 

 the apparently closely allied 7. coronopus, Defrance, a fossil form' 

 found at Grignon (M.-Ed. I. c, p. 23. pi. 12. fig. 3), the anterior 

 side of the branches rises in the middle into an acute ridge. 

 Taking also into consideration the wide diiFerence of locality, it 

 would appear quite certain that 7. atlantica and 7. radians, not- 

 withstanding their striking outward resemblance under certain 

 conditions of growth, are perfectly distinct species. 



2. Horner a, Lamx. 

 1. H.frondiculata, Lamx. PI. I. fig. 7 a. •? ,sjb«ft 



H.frondiculata, Lamx. Exp. Meth. p. 41. pi. 26. fig. 1, &pl. 74. 



figs. 7, 9; M.-Edwards, Sur les Crisies, p. 17- pi. 10. fig. 1 ; 



Blainville, Man. d'Actin. p. 419. 

 Retepora frondiculata, Lamarck, Hist. d. An. s. V. 2de edit. 



p. 277. 

 Millepora tuhiporUy Ellis & Soland. p. 139. pi. 26. fig. 1. 

 M. lichenoides, Linn. ; Pallas, Elenchus, p. 245 ; Esper, Mill. 



pi. 3. figs. 1-4. 

 Madrepore rameux, Marsigli, Hist, de la Mer, p. 49. pi. 33. 



figs. 162-164. 

 Var. a. H. affinisl M.-Edwards, /. c. pi. 10. figs. 1, 1 a. PI. I. 



fig. 7 h. 



The localities assigned to this species by Lamouroux are 

 Kamtschatka, the Indian and Australian Oceans, and the 



