266 THE VOYAGE OF H.M.S. CHALLENGER. 



membrane, not well defined, and of a granular texture (fig. 8) under a high power 

 indicating perhaps egg-cells. Of fully formed eggs, however, there were none, and the 

 lining membrane was not thrown into lobes or convolutions. If, however, the ovaries 

 were distended, and the pouches of the digestive cavity filled with matter, the general 

 appearance would approach that of Gorgonocephalus, except that the pouches would be 

 simpler ; and the ovaries would be much more restricted in area, unless, indeed, the lining 

 membrane of the body cavity to which the wall of the digestive cavity adheres has the 

 power to develop egg clusters, and thus form lobes, and push the digestive cavity inward 

 towards the mouth. 



It will be noticed that the genital openings are greatly distended, which shows that 

 the animal can contract or expand them, since, in other specimens, they were tightly 

 shut and reduced to a small slit. The attachments of the digestive cavity to the inner 

 open angle of the mouth frames are not so thick and muscular as in Gorgonocephalus, so 

 that the perihaemal canal is flattened, instead of more or less erect and rounded. Never- 

 theless there are the same ten radiating attachments respectively along the tops of the 

 arms and the middle of the interbrachial spaces, dividing the body cavity into ten com- 

 partments, which freely communicate at their inner ends by the perihaenial canal. In 

 the fining membrane of these compartments were found numerous fragments of micro- 

 scopic lime network (fig. 9) similar to that which exists in the walls of the bursa of 

 Ophiura Icevis and Ophiocoma scolopendrina. 1 It is these that, by their further growth, 

 make the thin scales which clothe the wall of the bursa in Ophiothamnus vicarius. 



A section of a species from an allied genus, Astrophyhyton costosum, showed a general 

 structure very like that of Gorgonocephalus. 



EuryaU aspera, Link. (PL XXXV. figs. 1-16; PL XLV. figs. 6-9). 



Euryaie aspera (asperum), Link., Hist. Anim. sans Vert., vol. ii. p. 538, 1816. 



Astrophyton scvtatum (pars), Linck, De Stell. Mar., pi. xx. fig. 32, 1733. 



Capitis medusae altera species minor supina, Seba, Thes., vol. iii., pi. ix., 1761. 



Astrophyton asperum, Agas., Mem. Soc. Scien. Nat. Neuehatel, vol. ii. p. 12, 1839 ; Mull. & Tr., 



Syst. Ast., p. 124; Lym., Proc. Bost. Soc. Nat. Hist., vol. xix., pL vi. 

 Astrophyton Icevipelle, Grube, Jahres-Berichte d. Sch. Gesell., p. 44, 1869. 



Station 186.— September 8, 1874; lat. 10° 30' S., long. 142° 18' E. ; 8 fathoms; 

 coral sand. Station 203.— October 3, 1874 ; lat, 11° 7' N., long. 123° 7' E. ; 12 to 20 

 fathoms ; mud. 



Trich aster. 



Trichaster, Agas., Mem. Soc. Scien. Nat. Neuehatel, vol. i., 1835. 

 A nearly smooth skin covers both disk and arms, whereof the latter fork a few times, 



J Hubert Ludwig, Beitrage zur Anatomie der Ophiuren, Zeitschr. fiir Wissenschaft, Zoolngie, Bel. xxxi., figs. 27, 28, 1878. 



