ECHINOIDEA. I. 51 



Ludwig has fonnd in this specimen, while lie has not seen this form in the other specimens. I shall 

 express no opinion whether it be otherwise the same species or not. 



Asthenosoma hystrix. The tube feet are placed in three dense series; a well developed sucking- 

 disk is found in the actinal tube feet. In the upper part of the tube foot the spicules are large, irre- 

 gular fenestrated piates quite inclosing the foot; in the lower part of the foot they are placed in two 

 distinctly separated series, and are more or less rod-shaped, with few holes (PI. XI. Fig. 29). The pri- 

 mary spines on the actinal side end in a little hoof. Only tridentate and triphyllous pedicellariæ are 

 found. Of tridentate pedicellariæ two forms are found, not very sharply distinguished. In the larger 

 form (PL XI\'. Fig. 26) the edges of the blade are involuted, only the point is a little widened, with a 

 remarkably irregular, finely serrate edge. In the smaller form (PI. XIII. Figs. 17 — 18) the involuted 

 part of the blade is shorter, the widened part comparatively larger and less irregular in the edge; 

 when the pedicellaria is shut, the valves are far less separated below than in the larger form (see 

 Wyv. Thomson: Porcupine -Ech. PL LXIV. Fig. 5). This form occurs in ver>- varying sizes. In the 

 triphyllous pedicellariæ the cover-plate is highh- developed, with a few, large holes along the 

 median line; the edge finely serrate (PI. XII. Fig. 34). The stalk of the pedicellariæ of the common 

 structure. 



It is evident that this species is not nearly allied to Astlicnosoiua, as here limited. Accordingly 

 it must form a separate genus keeping the name of Cahcria, which was originally given to it b>- 

 Wyv. Thomson, and which it has unjustly been deprived of. To the same genus Ast/iciiosoi/ia 

 gracilc A. Agass. will further have to be referred. Its pedicellariæ (PI- XIII. Fig. 3) agree so exactly 

 with those of C. Iiystrix^ that no distinct specific difference seems to be found in this feature; only 

 the smaller form of tridentate pedicellariæ is a little .sienderer than in C. Iiystrix. The primary spines 

 end in a small hoof as in C. Iiystrix\ the tube feet are arranged in the same way as in this latter. 

 The spicules are rather large, irregular fenestrated piates; in the lower part of the tube foot they are 

 smaller and arranged in two well separated series, in the upper part they join completely, and form a 

 close mail round the foot, as figured by Wyv. Thomson from C //i'j/'r/.^ ( Porcupine -Ech. PI. LXIV. 

 Fig. 3). The sucking disk well developed. — Agassiz, who has seen, to be sure, that this .species is 

 verv similar to C. Jiysfrix, mentions in his description of it (Chall. Ech. p. 98) some peculiarities with 

 regard to the arrangement of the tubercles as special characters > ; in pedicellariæ and tube feet no 

 distinct specific difference seems to be found, so that for the present we must rest satisfied with the 

 .statements of Agassiz. 



I discovered a very interesting feature by the examination of the type specimen of this species. 

 Some of the secondary spines were swollen at the point (PI. XIV. Fig. 27), and in the 

 swollen part proved to be sitting a little parasitic Copepod. This seems to be a case of 

 parasitism hitherto quite unknown, and in interest .scarcely below that found by Koehler: the gall- 

 forming, parasitic Copepoda in PlwrinosoDia iiraiius-. (229)'). 



The characters here mentioned for Calvcria gracilis as well as the mentioned feature of the 

 parasitic Copepod, apply only to the specimen from Chall. st. 200. — Of some specimens from sts. 184 

 and 219 Agassiz says that he refers them to this .species cwith considerable doubt , in which he is 



I) The parasite will be ilescrilieil by Dr. H. I. Hansen in Viden.sk. Medd. fra Nat. Foren. Kobenhavn. 



