170 Proceedings of the Royal Physical Society. 



interesting in that it is of a somewhat simpler type than even 0. puncto- 

 coertcleum, which bad already helped considerably to bridge the gulf between 

 the genus Ophiothrix and the genus Ophiopteron, as exemplified in the 

 complex structure of 0. elegans. 



The new species essentially agrees with the other species of Ophiopteron 

 iu having some of the arm-spines on several of the arm -joints united by a 

 membrane, thus entitling it to be considered a true Ophiopteron. But while 

 0. elegans and 0. sibogae have the disc covered with short spines, and while 

 0. puncto-coeruleum has the radial shields naked and the remainder of the 

 dorsal side of the disc covered with spines, this new species has no spines on 

 any part of the upper surface of the disc. 0. gymnatuin has large radial 

 shields and a very distinct centro-dorsal plate, and these, as well as the 

 smaller disc-scales, are naked and slightly roughened with very fine 

 granulations. The disc appearance undoubtedly closely resembles that of an 

 Ophiothrix, and is, indeed, very similar to that of 0. martensi Lyman. 



Professor Koehler, to whom I submitted this unique specimen, most 

 kindly sent me the following note regarding it : — 



" It is indeed a new species of Ophiopteron, neighbouring to 0. puncto- 

 coerideum, which it recalls by the expansions which are found only on the 

 spines near the base of the arm, but it differs therefrom, in respect of the 

 coloration, the presence of more arm-spines, the absence of spines on the 

 disc, etc." 



Loccdity. — St. XXII., Hastings Harbour, St Luke's Island, 3 to 20 fathoms 

 and shore, rock and sand (one example). 



(15) Lutkenia cataphracta Brock, 1888. 



This species is represented by a single example. To the description 

 given by Brock, who first established the genus, which is very closely allied 

 to the genus Ophiomaza, and to the couple of wholly admirable figures given 

 by Koehler (1904, figs. 92, 93), who first illustrated this species, there is 

 little to be added. The main point is that on the interbrachial ventral 

 surface the scales are more numerous than represented in Koehler's diagram, 

 and Koehler's own comment on confirming my identification of this 

 individual is that " the chief difference consists in the ventral plates of the 

 disc being a little smaller than in the type." 



My example has a disc-diameter of 6 mm., and while the length of the 

 longest arm is 19 mm., the shortest complete one is only 8 mm. There are 

 five short stout conical arm-spines, and towards the tip of the arm the lowest 

 miii is hooked or lias a hooked projection. There is a narrow indigo coloured 



