82 Mr. F. Chapman on Pulytrenia planum. 



anterior border of eye ; a strong erectile spine below the nostril; 

 4 spines at anglo of pra^opcrcU% upi)er very strong. Dorsal and 

 anal confluent with caudal, which is pointed ; D. XXXI 150; 

 spines short; distance between first spine and head § length 

 of latter; A. II 150. Pectoral ^ length of head. Scales 

 very small, 15 between origin of soft dorsal and lateral line. 

 Brownish, marked with darker. 



Total length 200 millim. 



Stanley Pool, Congo. Collected by Mr. Greshoff. The 

 specimen, now in the British Museum, through the kindness 

 of Prof. Hubrecht, had been provision;illy referred to M. crypta- 

 canthus,Qr[\\Y., by Mile. Schilthuis (Tijdschr. Nederl. Dierk. 

 Ver. [2] iii. 1891, p. 84). 



XIIT. — On the Identity of Polytrema planum of Carter with 

 P. miniaceum var. involva. By Frederick Chapman, 

 A.L.S., F.R.M.S. 



In the Ann. & xMag. Nat. Hist, for 1876 Dr. H. J. Carter 

 figured and described * a species of Polytrema found encrusting 

 old corals, which he compared with a spreading Melobe.sia in 

 its habit of growth. In the following year f the same author 

 described other specimens of a similar organism showing a 

 more advanced stage of growth ; and observing a relation- 

 ship between the structure of this and certain adiierent types 

 of Gypsina^ he proposed to drop the former name, both 

 generic and specific (a method opposed to accepted rules of 

 nomenclature), and to re-name the form Gypsina melohesi- 

 oides. The last-named specimens Carter did not figure. A 

 few weeks ago, however, by the kind assistance of Prof. 

 Jeffrey Bell, I was so fortunate as to find, in the Zoological 

 Department of the Natural History Museum, C;irter's type 

 specimen, labelled Gypsina melubesioides. This specimen 

 has encrusted the lower part of a sponge from Mauritius. 



The enveloping form of Polytrema which has been found 

 in such abundance in tiie rocks and reef- deposits of the atoll 

 of Funafuti, and to which I had given the name Polytrema 

 miniaceum var. involva, is identical with Carter's type 

 specimen. This identification could not be satisfactorily 

 established from the meagre figure of Polytrema planum 

 which Carter gives, whilst his reference to the mature 



* Ser. 4, vol. xvii. pp. 211, 212, pi. xiii. fig.-^. 18, 19. 

 t Ibid. ser. 4, vol. xx. p. 172. 



