Mr. J. D. Macdonald on a new species of Asteroid Polypes. 3M 



Both Bowerbankia and Vesicularia agree in the uniserial and uni- 

 lateral distribution of the polypes, but in the present instance the 

 cells are arranged in linear and bilateral clusters. 



XXXII. — Anatomical Description of a Species of Asteroid Po- 

 lypes, probably forming the type of a new genus of Alcyonidce. 

 By John Denis Macdonald, Assistant Surgeon R.N.* 



On leaving the Conway Reef (lat. 21° 44' 48" S., long. 174° 37' 

 45" E.), July 4, 18.55, a very beautiful branched asteroid Zoophyte, 

 belonging to the Alcyonidfie, was brought up from a depth of between 

 30 and 40 fathoms, on the buoy-rope of the anchor. 



The polypidom, from a trunk of about one inch and a half in 

 diameter, branched off, with much irregularity, but generally in a 

 dichotomous manner, into very minute subdivisions. 



The investing membrane was strengthened by the close deposition 

 of elongated, fusiform, and minutely tuberculated spicula of a deep 

 crimson-lake tint, which impart their colour to the whole mass. 



The internal substance was chiefly composed of longitudinal mus- 

 cular septa, radiating from the central axis (which contained no 

 denser material), frequently communicating with one another late- 

 rally, and being fixed into the internal surface of the integument in 

 vertical lines. These muscular septa were invested on each side with 

 a layer of finely reticulated vessels ; both sets being connected by 

 numerous transverse trunks passing through the intervening muscular 

 tissue, and the spaces between the septa were filled with a transparent 

 glairy fluid. 



The polyp-cells were exposed and solitary, resting on the internal 

 surface of short branchlets strengthened by large dorsal spicula, one 

 of which, much larger than the rest, extended considerably beyond 

 the polyp-cells, tapering gently to a needle-like point. These latter 

 spicula are covered with tubercles, and in every respect but in size 

 similar to those of the general integument. 



The small spicula on the internal or ventral surface of the branch- 

 lets diverge from one another in the peripheral direction, while those 

 on the dorsal border are disposed longitudinally. 



The mouth of each cup-like polyp-cell was surrounded with about 

 eight projecting spicula, whose fixed extremities were curved up- 

 wards and inwards, festoon-fashion, while numerous smaller ones 

 were so disposed as to fill up the open spaces posteriorly, and thus 

 strengthen the body of the cell. 



Although I have not been able to count the number of the oral 

 tentacula satisfactorily, from their proportional size I can readily 

 believe that there were about eight in this species, as in most if not 

 all other asteroid polypes. They were broad and flat, tapering to a 

 blunt point, like those of Sarcodictyon (Forbes), to which genus I 

 have no doubt this Zoophyte is nearly allied, though the habit of the 

 polypidom is so very diff'erent. 



* From the Proceedings of the Royal Society, March 12, 1857. 



