176 



ECHINOIDEA. I. 



— Tetradactylous pedicellariæ I have not found. The tridentate and triphyllous pedicellariæ as in 

 fenesfratiiiii\ the large form of tridentate pedicellariæ is found in very different sizes, but also the 

 small enes are of the typical structure, so that they cannot be confounded with the otlier form. 

 Besides the forms of the second kind of tridentate pedicellariæ mentioned and figured for fenestratuin, 

 a form is also found here where the blade is not at all involved below (Fig. 10). I have, however, 

 once found this form in A. fi iirstrafni/i (in a specimen from Barbados, in British Museum), and so it 

 can be no specific character. The spicules, perhaps, are a little smaller than in fenestrafnm, but this 

 difference is too little marked to be used as a specific character. The best character is the colour, 

 which in the preserved specimens is deeply dark violet, while all the specimens of fencstratitiii I have 

 seen, are quite bleached in aicohol: also in the living animals the colour is quite different — comp. 

 the description by Wyv. Thomson. The primary spines on the actinal side are dark with a rather 



large, white hoof, very conspicuous on the dark 

 ground-colour. — The organs of Stewart are very 

 large; the longitudinal muscles powerful. — For 

 this species, the place of which is evidentlv 

 between A. foiestrattuii and cnn'acaii/i, I propose 

 the name of Aræosoma violaceum n. sp. 



Echinosoina uraiiits (p. 57). A couple of speci- 

 mens of this species (< Talisman Sahara, 938 m.) 

 I have seen in the museum of Paris. All the 

 primary spines on the actinal side were broken, 

 but some of the spines round the mouth had a 

 little hoof; after this there can be no doubt that 

 the primary spines on the actinal side end in a 

 hoof as in E. touic. The large tridentate pedicel- 

 lariæ are quite similar to the one of E tcnuc 

 figured on PI. XII. Fig. 35, with the e.Kception that 

 here the apophysis does not continue into the 

 blade as a crest. 

 Hygrosoma Prtcrsii (p. 59). In a specimen of this species (the Azores, 1258 m. sTalisman-. 

 The museum of Paris) was found a pedicellaria (Fig. 11) forming a transition between the ophicephal- 

 ons pedicellariæ in Troinikosoma KoeJihri and the short, thick pedicellariæ of //. lucnlriituni. After 

 this there can be no doubt that litculciitiim is really to be classed together with //. Pffcrsii\ and it 

 may well be supposed that this form of pedicellariæ will also be found in //. hoplacanflia — in other 

 words that it is one of the characters of the genus Hygroso/jin. Whether it is then to be regarded as 

 an ophicephalous or a transformed tridentate pedicellaria is so far of no consequence; I think it, 

 however, most correct to regard it as an ophicephalous one, although in litaileutuni it is not of the 

 typical structure. — The form of pedicellariæ in //. luculcntum (Chall. PI. XLIV. Fig. 27) mentioned on 

 p. 60, I have not been able to find b>- a renewed examination of the specimen from st. 200, although 

 this specimen is rather well preserved. — If thus ophicephalous pedicellariæ are found in the genus 



Fig. 10. 



Fig. II. 



Fig. 10. Valve of tridentate pedicellaria of Aræosoma violaceum. 



Obj. AA. Oc. II. (Zeiss). 

 Fig. II. Valve of ophicephalous pedicellaria of Hygrosoma 



Petersii. Obj. AA. Oc. I. (Zeiss). 



