20 THE VOYAGE OF H.M.S. CHALLENGER. 



Retepora atlantica, Busk. 



Retepora atlantica, Busk, Zool. Chall. Exp., part xxx. p. 116, pi. xxviii. fig. 1. 



This, which I should prefer to call Retepora marsupiata, Smitt, has the pore placed 

 liigher up than in Retepora Jissa. so that the characteristic groove is wanting, but the two 

 are closely allied, and it would be well to group Retepora atlantica, Retepora marsupiata, 

 Retepora Jissa, &c., round Retepora Jissa, in the same way that MacGillivray has made 

 various varieties of Retepora monilifera. Many of the Reteporw are specifically 

 separated on very slight grounds. 



On the dorsal surface of Retepora atlantica there are numerous apiculate avicularia, 

 usually one to each vibicated area, and besides there are numerous small round avicu- 

 laria. 



This is abundant in the washings of the dredge between Fayal and Pico. 



Retepora monilifera, MacGillivray, form munita, Hincks. 



Retepora monilifera, var. munita, Hincks, Ann. and Mag. Nat. Hist., ser. 5, vol. i. p. 361, 



pi. six. fig. 5. 

 Setepora monilifera, form munita, MacGillivray, Trans. Eoy. Soc. Vict., vol. xx. p. 108, pi. i. 



fig. 3 ; pi. ii. fig. 3 ; Zool. of Vict., dec. x. p. 22, pi. 96, figs. 4, 8. 

 Retepora victoriensis. Busk, Zool. Cliall. Exp., part xxx. p. 117, pi. xxvii. fig. 7. 



The specimen examined was from Station 162, 38 to 40 fathoms, but was evidently 

 dead when dredged, and I have therefore not been able to make a detailed comparison. 



Retepora monilifera, MacGillivray, form umhonata, MacGillivray. 



Retepora monilifera, MacGillivray, form umhonata, MacGillivray, Zool. of Victoria, dec. x. p. 23, 



pi. 97, figs. 1-3. 

 Retepora hirsuta. Busk, Zool. Chall. Exp., part xxx. p. 119, pi. xxvi. fig. 4. 



The Challenger specimen has the ovicell strongly umbonate, and the dorsal surface has 

 vibices, usually with a line from a fenestra to each of those surrounding it. 



Retepora contortuplicata, Busk. 



Retepora contortuplicata, Busk, Zool. Chall. Exp., part xxx. p. 120, pi. xxvi. fig. 2. 



On the dorsal surface small round avicularia are not common, but can be seen 

 occasionally, and on the anterior surface, besides the triangular avicularia, there are small 

 oval ones. 



Retepora columnifera, Busk (PI. III. figs. 10, 11). 



Retepiora columnifera. Busk, Zool. Chall. Exp., part xxx. p. 122, pi. xxvi. fig. 5. 

 This species receives its name from the " solid columnar dorsal processes " by means 

 of which it is attached, but these calcareous attachment processes are by no means 



