ECHINOIDEA. I. 



last almost mystical Calveria fcnestrata has here been refound. It proves, into the bargain, to be common 

 enough, and has only been missed, because it has been confounded with Calveria hystrix. The exceed- 

 ingly remarkable tetradactylous pedicellariae, 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 found quite wanting some kind of pedicellariae normally found 

 in the species, -- for instance globiferous pedicellariae in Echinus Alexandri}. To be sure, the differ- 

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

 exactly the details of this difference, we shall be much 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 fact that A. fenestratum is far more robust 

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

 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 pedicellariae that we find sure characters. As 

 the pedicellariae 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 thorough description of this species is not necessary here, any more than with regard to 

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

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

 A. Rcyiwldsii}. 



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

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

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

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

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

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



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

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

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

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

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

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

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

 The blade is filled by a rather coarse net of meshes. The valves are very wide apart when the pedi- 

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

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

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

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

 is comparatively larger, and the edge not so deeply sinuate. In the smallest ones the valves are 

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



The Ingolf-Eipcdition. IV. I. Io 



