86 



TH. MORTENSEN, 



(Schwed. Siidpolar-Exp. 



Abatus Agassizii (PFEFFER). 

 PI. X, Figs, i, 3, 5, 9, 14. PI. XIX, Fig. 40. 



Hemiaster cavernosas A. Agassiz. 1872. Revision of Echini, p. 587. PL XXI. c. figs. I — 2. 



— australis — — — — 586. — ■ — 3. 



— cavernosas G. Pfeffer. 1889. Zur Fauna von Siid-Georgien. Jahrb. d. Hamb. wiss. Anst. VI. 



p. 49. 



— Agassizii PFEFFER. M. S. 



— cavernosas MEISSNER. 1900. Echinoidea d. Hamb. Magalh. Sammelreise, p. 13 — 14. 



? — elongatus Koehler. 1908. Asteries, Ophiures et Echinides de l'Exped. antarct. nat. Ecoss. 

 Trans. R. Soc. Edinb. XLVI, p. 618. PI. XVI, figs. 145 — 158. 



This species differs in some respects markedly from cavernosas and PJiilippii, 

 and it seems scarcely doubtful that it is a distinct species; in any case it must be 

 kept separate from cavernosus or P/iilippii, even if it may ultimately prove that it 

 deserves only to rank as a variety of cavernosus. — It seems highly probable that 

 it was this species which Agassiz described and figured under the name of Hemi- 

 aster cavernosas and anstralis in the »Revision of Echinb; the photographic figures 

 given there agree very closely with the typical A. Agassizii, as will be seen on 

 comparing them with the figures given here. (On account of this De LORIOE, on 

 having the true cavernosus before him and seeing that it differed from H. cavernosas 

 of the »Revision», described it as a new species, H. gallegosensis.) It further seems 

 not improbable that the H. elongatus recently described by KOEHLER (Op. cit.) is 

 identical with this species. Unfortunately the otherwise very elaborate description 

 does not give any information of the subanal tubefeet; a communcaition from my side 

 to the Scottish Oceanographical Laboratory in Edinburgh, where the material is pre- 

 served, has not been answered, so that I am unable to give information on the point 

 in question, and I must therefore leave it undecided, whether elongatus is identical 

 with Agassizii or a separate species. 



The shape of the test (PI. X. Figs. 5, 9) is upon the whole like that of cordatus 

 (cf. PI. XVIII. Figs. 2, 4, 16, 20 of »Die Echinoiden d. deutschen Siidpolar-Exped.), 

 it only affords one marked distinguishing feature, viz. in the odd anterior ambulacrum 

 being flush with the test at the front end. On the abactinal side, inside the fasciole, 

 it is slightly sunken. The posterior petals are as long as, or even longer than, the 

 anterior ones; only in one specimen (from Stat. 33) I find the posterior petals 

 slightly shorter than the anterior; the latter are directed more sidewards than is 

 generally the case in cavernosus. The apical system is central, as is also the vertex, 

 the test sloping from here towards both ends. The subanal tubefeet are rudimentary 

 as in cordatus, only in the specimen from Stat. 33 one tubefoot is developed on 

 one side. The peristome is somewhat larger than in the other species, sometimes 

 even very large. Along the border of the labrum small spines and rather numerous 



