684 Reports on the Zoological Collectmv^ made in Torres Straits, 1888—1889. 



It seems probable that the two genera are coterminous, and, if so, /. cliftoni 

 will rank as a second Australian species of Isaurus. 



In 1877 Andres described (p. 226) a new genus and species, Panceria spongiosum 

 from Port Natal; but in 1884 (p. 315) he abandoned the genus, and re-named it 

 Polythoa (^Monothoa) spongiosa. We regard this as belonging to the genus under 

 discussion. 



TOREES STRAITS SPECIES OF THE GENUS ISAURUS. 

 /. asgmmetricus, n. sp. 



Isaurus asymmetricus, n. sp. 

 (PI. Lxi., figs. 7-9; PI. LxiL, fig. 4 ; PL lxiii., figs. 4-6 ; PI. lxiv., fig. 9.) 



Form. — Body elongated; upper portion of column, in retracted specimens, 

 with usually four rather irregular longitudinal rows of tubercles, arranged in such 

 a manner that there is a longitudinal area free from them. In some specimens 

 there are intermediate tubercles, which may even form one or two rows. Young 

 specimens are entirely smooth. The smooth side is somewhat shoi'ter than the 

 tuberculated, so that the body bends over to the former, and the introverted 

 mouth is rarely terminal. The contracted cajDitulum exhibits radiating furrows 

 from 18 in number upwards. 



The polyps grow either singly or in small clusters. In the latter case there 

 is a common, firm, fleshy, incrusting coenenchyme, occasionally forming stolons, 

 from which new buds arise. 



Colour. — Whitish below, passing into brownish above; the darker portion is 

 variously mottled with cream, or greenish cream, and occasionally diversified with 

 darker spots ; the tubercles are somewhat pinkish in colour. 



Dimensions. — Average size of retracted specimens, 45 mm. in length ; greatest 

 diameter, 7 mm. The longest specimen measured 56 mm. in length when 

 retracted. 



Locality. — Torres Straits ; on fringing reef between tides, Mabuiag, Oct., 1888, 

 numerous specimens ; 15—20 fathoms, between reefs, Murray Islands, Jan. 5, 

 1889, two specimens. 



The specific name is derived from the marked asymmetry of the polyp. It is 

 undoubtedly nearly allied to the Mammillifera tuberculata of M'Murrich 

 (1889, p. 117). The specific differences are the lesser number and greater size of 

 the tubercles, though their diameter is about the same, and their asymmetrical ar- 

 rangement; the height of our species is about double that of the West Indian form. 



