ECHINOIDEA. II. 



105 



of the test of this species. But it seems beyond doubt that in the Challenger* Report two separate 

 forms were included under Hemiaster zonalusv. one (St. 8), evidently the figured one, a true Plemiaster 

 and even the same as H. expergilus, the other (St. 126) probably a Schizaster, which will certainly 

 prove to be a new species. The name Hemiaster zonatus ought then certainly to be dropped as a 

 synonym of H. expergitus. 



Hemiaster Mentzi A. Ag. has unfortunately not been figured by Professor Agassi z, and from 

 the description (< Blake-Echini. p. 66) it is quite impossible to see by which characters it is disting- 

 uished from //. expcrgitus, the only feature not agreeing very well with the latter species being the 

 narrow, comparatively elongate space included within the peripetalous fascicle*. From the U. S. 

 National Museum I have received for examination a large specimen of H. Mentzi; it is certainly 

 identical with H. expergitus. Of course, I cannot state with certainty that it is the true H. Mentzi, I 

 have seen; but I have no reason to doubt the identification. Until the contrary is proved I must 

 then regard 77. Mcntzi as a synonym only of H. expcrgitus. From H. gibbosus it is stated to differ 

 in having a larger number of buccal plates, a feature which I do not find to hold good by comparing 

 the specimen of gibbosiis from the Siboga with the specimen of H. Mcntzi or with expcrgitus. 



Hemiaster florigerus Studer differs from expcrgitus in several respects, judging from the de- 

 scription and figures given by Studer (Echinoidea d. Gazelle. (386) p. 882. Taf. II. 3). The test is 

 broadest in the middle, not in the anterior end as in expergitus, and the height of the posterior end 

 is evidently smaller than in the latter species. 1 According to the description the anterior petals are 

 the shorter, but this is in contradiction to the figures 3 a and 3 c. The apical system, according to 

 the Fig. 3 d, is ethmolytic, a very important character, so important, indeed, that it must certainly 

 exclude the species from the genus Plemiaster. (Dr. Meissner kindly informs me that Studer's 

 description of the apical system is correct). The two anterior genital pores are 

 distinctly smaller than the posterior: in expcrgitus they are of equal size. The 

 relation of the labrum to the adjoining ambulacra cannot be seen from the figures; 

 but Dr. Meissner informs me that the labrum ends off the first ambulacral plate. 

 (Fig. 20). By a short examination of the type-specimen during a visit to the Berlin- 

 Museum I found two sorts of pedicellariae, viz. tridentate and rostrate. The former 



Fig. 20. Labrum and 



(PI. XV. Fig. 23) are essentially like the large form of tridentate pedicellarise in adjacent ambulacral 

 expergitiis, but only o - 2 mm . The rostrate pedicellarise differ only very little from the ^ a f ts 

 form with the small end-part of expergitus. The spicules of the frontal tube-feet sketch by Dr. M. 

 (PI. XV. Fig. 28) are more numerous, larger and more thorny than those of exper- 

 gitus. They are arranged in two close series; on one side those of both series have their ends inter- 

 mingled, on the other side they leave a bare space between them - - just as has been described and 

 figured for Dorocidaris papillata (Part I. p. 33. PI. VIII. Fig. i). That H. florigerus is a distinct species 

 is beyond doubt, but it is very doubtful if it can remain in the genus Hemiaster, on account of its 

 ethmolytic apical system. However, as long as the species is so unsufficiently known it will scarcely 

 be possible to determine with certainty to which genus it ought to be referred. 



1 Studer gives the following measurements: Length 24 mm , Breadth 21""", Height I3 mm . In //. expergilus of a corre- 

 sponding size the measurements are: Length 2o n " n , Breadth 2o mm , Height i6'5'"' n . 



The Ingolf-Expedition. IV. 2. 14 



