82 Mr. F. Chapman on Polytrema planum. 
anterior border of eye; a strong erectile spine below the nostril ; 
4 spines at angle of preopercle, upper very strong. Dorsal and 
anal confluent with caudal, which is pointed ; D. XX XI 150; 
spines short; distance between first spine and head ? length 
of latter; A. II 150. Pectoral 4 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 provisionally referred to M. crypta- 
canthus, Gthr., by Mile. Schilthuis (Tijdschr. Nederl. Dierk. 
Vero (2) nil ool p64). 
XIIJ.—On the Identity of Polytrema planum of Carter with 
P. miniaceum var. involva. By FREDERICK CHAPMAN, 
An.) RMS: 
In the Ann. & Mag. Nat. Hist. for 1876 Dr. H. J. Carter 
fizured and described * a species of Polytrema found encrusting 
old corals, which he compared with a spreading Me/obesia in 
its habit of growth. In the following year T the same author 
described other specimens of a similar organism showing a 
more advanced stage of growth; and observing a relation- 
slip between the structure of this and certain adherent 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 melobest- 
oides. ‘Che 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, Carter’s type 
specimen, labelled Gypsina melobesioides. his specimen 
has encrusted the lower part of a sponge from Mauritius. 
The enveloping form of Polytrema which has been found 
in such abundance in the rocks and reef-deposits of the atoll 
of Funafuti, and to which I had given the name Polytrema 
miniaceum var. tinvolva, 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, pl. xiii. figs. 18, 19. 
} Ibid. ser. 4, vol. xx. p. 172. 
