ECHINOIDEA. I. 



73 



last almost mystical Cahcria fcucstrata has here been refouiid. It proves, into the bargain, to be comraon 

 enoiigh, and has oiily been missed, because it has been confonnded with Calveria hysfrix. The exceed- 

 ingly remarkable tetradactylous pedicellariæ, which would be an excellent character of this species, 

 seem generally to be wanting, probably broken off, possibly originally wanting in some specimens (as 

 in other Echinids individuals are often fonnd quite wanting some kind of pedicellariæ normally fonnd 

 in the species, — for instance globiferous pedicellariæ in Ecliiuus ^l/cxaiidri). To be snre, the differ- 

 ence between the two species with regard to their habitns is considerable ; but if we examine more 

 exactly the details of this difference, we shall be miich surprised to find a great conformity in almost 

 all external features, above all in the arrangement of the tubercles. No other difference can in reality 

 be given with regard to the common appearance than the faet that A. /cnestrafuni is far more robust 

 than Calveria hysfrix, and that the colour is different. The great difference in the form of the piates 

 in the two species emphasized by Wyv. Thomson as a chief character, is only to be seen in dried 

 specimens, and, strictly speaking, only from the inside; it is moreover, as shown by Bell (op. cit.), 

 subject to great variation. It is only by examining the pedicellariæ that we find sure characters. As 

 the pedicellariæ have not hitherto been taken into consideration, there is, so far, a good excuse of the 

 fault committed by the confounding of the two species. 



A tliorough description of this species is not necessary here, any more than with regard to 

 the two precediug ones; I shall only make some supplementary remarks, and for the rest the reader 

 is referred to the descriptions by Wyv. Thomson and Agassiz (the latter one to be found under 

 A. Rcyiio/dsii ). 



The primary spiues of the actinal side end in a small, short, and rather broad hoof; this I take 

 to be what Agassiz means by calling theni trumpet-shaped . The structure is as in Calveria hysfrix, 

 only that the spines seem here always to be smooth, while in C. hysfrix they are more or less thorny. 

 (Transverse section. PI. XI. Fig. 8). The spicules are large, irregular fenestrated piates, which in the 

 outer part of the tube foot encompass it completeh"; in the lower part they are somewhat smaller, and 

 are arranged in four longitudinal series. Sucking disk well developed. 



The tetradactylous pedicellariæ I have not seen, but as in A. coriacniiii they are quite similar 

 to those figured by Wyv. Thomson for A. fenestralin/i, it may be considered rather certain that no 

 specific characters are found in them. Such characters are, on the contrary, found in the tridentate 

 pedicellariæ, as shown above. There are two forms of tridentate pedicellariæ. In the larger form, 

 which has been overlooked by Wyv. Thomson, but which I have found in the mentioned t\pe 

 specimen, the blade is much involuted and curved outward. The point is somewhat widened, and has 

 two deep sinuations in the edge on each side (PL XIV. Fig. 32), but the edge is otherwise not indented. 

 The blade is filled b\- a rather coarse net of meshes. The \-aIves are very wide apart when the pedi- 

 cellaria is shut. The base is especially large, so that there is room for a great man)- muscular fibres; 

 no doubt these pedicellariæ are very powerful. The head has a length of up to 2""", the neck is quite 

 short. — The smaller form is very much varying as to size and form; the larger ones fPl. XIV. Fig.24) 

 recall the large form very much, but the val ves are much less curved, the widened part of the point 

 is comparativel}' larger, and the edge not so deeply sinuate. In the smallest ones the val ves are 

 almost not separated, and the edge is almost quite straight. Wyv. Thomson has figured one of 



The Ingolf-Expedition. IV. I. lo 



