117 



circle around the primary one. Between each two adjoining jnimary interambulacral 

 tubercles there is (on the abactinal side) a narrow, slightly elevated ridge with a 

 small tubercle on the middle, connecting the primary tubercles. In the ambulacra 

 such a ridge may be laintly indicated. The median space, in both areas, is bare and 

 a little sunken: it is rather large in the interambulacra. The apical system is like 

 that of G. pulchellus. The spines are slender, those at the ambitus the longest, 

 c. Va of the diameter of the test; the primary ones smooth, the secondary thorny; 

 the actinal spines are not widened or curved. The auricules are low processes, 

 which do not meet above to form an arc. The mouthslits are small but sharp. 

 The buccal membrane has no plates in the mouth edge, but rather numerous small 

 bihamate spicules (PI. VII. Fig. 24. a) are found spread in the whole membrane; in 

 the gills such spicules occur in great numbers together with the usual irregular 

 plates. The tubefeet contain rather numerous small, very little curved, bihamate 

 spicules (PI. VII. Fig. 24 c.). The globiferous pedicellariæ present the shape usual 

 in this genus; they have small glands on the stalk. Numerous small bowshaped 

 spicules (PI. VII. Fig. 24 d.) are found in them. The tridentate pedicellariæ are very 

 characteristic (PI. VII. Fig. 30); the blade is almost Hat, narrow, widened in the 

 outer part; the edge is smooth and in the outer part exceedingly finely serrate. The 

 valves are a little curved and join only with the outer part. The neck is rather short. 

 The ophicephalous pedicellariæ do not present any special characters; the triphyllous 

 ones (PI. VII. Fig. 26) diller somewhat in shape from those of G. pulchellus, the 

 blade being less widened. The stalk and neck of these pedicellariæ contain 

 numerous very small bihamate spicules (PI. VII. Fig. 24. b.). — The colour of the 

 lest is wholly white, or with a taint brownish tint on the bare spaces. The spines 

 are banded with 1 — 3 bands of red; in the lower part they are green or white, both 

 types of colorations occurring in the same specimen. The base of the spines is red. 



This beautiful species belongs to the group of G. Robillardi, distinguished 

 by its remarkable oblique apical area; to the same group the species G. p«nn7(o de 

 Meijere ') seemed to belong. Through the kindness of Dr. de Meuere, however, I 

 have had a specimen for examination, and I must state that it is no Gtjnmechinus, 

 but a Psammechinus, and that it is the species described by Bell (Echinoderms of 

 Macclesfield Bank) as „Salmacis" rufa (see below p. 122). 



Gijmnechinus darnleijensis (Woods) dilTers very markedly from all the species 

 mentioned above in having a regular apical system with no ocular plates reaching 

 the periproct (comp, above p. 116). In the „Ingolf"-Echinoidea (p. 110) I have stated 

 that the auriculæ are of the usual form (according to a communication from Prof. 

 Bell in a letter to me), as opposed to the statement of Woods-') that they are slight thin 

 processes, which do not meet. Having reexamined the specimens in the British Museum 



') „Siboga"-Echinoidea. p. 90 



') The Echini of Australia Proc. Linn. Soc. N. S. Wales. II. 1878. p. 165. 



