76 



ECHINOIDEA. I. 



latter is very large and broad, and the pores spread also over some of the small piates inside of it. 

 Koehler savs that the madreporite is triangnlar, very large, and prolonged; his fignre does not show 

 this, there it is scarcely larger than the other genital piates. — The genital openings are covered 

 by a large genital j^apilla, 3—4™™ Ion g, resembling a tube foot. Prof. Koehler informs me that 

 a similar formation was found in his specimens; he has seen traces of it on some of the piates; but 

 as his specimens were badly preserved he could not distinguish the nature of these traces with cer- 

 tainty, but took them to be loosened pieces of skin. Af ter having seen my drawing he feels certain 

 that they were the genital papillæ. — A similar formation is mentioned by de L o r i o 1 (246 p. 369) in 

 the specimen he (wrongly) takes to be a young AstJieiiosoma van'iiin: les pores génitaux sont tres 

 grands, circulaires, couverts d'une fine membrane au milieu de laquelle saillit la papille genitales ; for 

 the rest de L or i ol has no further remarks of this peculiar formation. 



Neither with regard to the spines of the dorsal side does this specimen quite agree with the 

 description of Koehler: Dans les zones interambulacraires les tubercules primaires forment, vers le 

 milieu de chaque rangée de plaques, une file assez reguliére qui s'étend jusqu'å une petite distance 

 du périprocte, mais toiates les plaques interambulacraires ne portent pas de ces tubercules primaires* 

 (p. 19). Here they do not at all form a regular series, are on the contrary placed very irregularly. 

 According to Koehler the spines are much shorter on the abactinal side than on the actinal side ; 

 in the specimen in hånd the faet seems not to have been so. To be sure all the primary spines on 

 the abactinal side are broken, but to judge from the fragments kept, they must have been of about 

 the same length as the primary spines on the actinal side. As observed by Koehler, the abactinal 

 side looks rather naked here being far fewer spines than on the actinal side. — The structure of the 

 spines is the common beautifnl one: regularly perforated tubes with raised longitudinal ridges, ending 

 in a fine point. Transverse sections of the large primary spines from tlie actinal side (PI. XI. Fig. 9 a) 

 show the longitudinal ridges highly developed, with the outer surface widened, so that their edges 

 join completely; they are ranch hollowed aloug the median line; secondary connecting bearas between 

 the longitudinal ridges may be more or less developed. The small spines on the abactinal side are 

 also provided with strong longitudinal ridges, with widened outer surface, and hollowed along the 

 median line (PI. XI. Fig. 9 b). The primary spines on the actinal side as also the spines of the peristome 

 are somewhat thorny, the abactinal ones are quite smooth. 



Koehler gives a figure of a whole tridentate pedicellaria, but he gives no informations of 

 the structure of the blade except the one thing that the edge is not serrate — and this is scarcely 

 correct, at all events it does not apply to the specimen in hånd. In the largest pedicellariæ (the head 

 of a length of up to 2""") the valves are very broad and flat, and join completely, when the pedicel- 

 laria is closed (PI. XIV. Fig. 33). The widenings from the upper end of the apophysis reach almost or 

 quite to the edge of the blade, which is not involuted; in the outer part of the blade the edge is 

 somewhat sinuate. The blade is filled by a very complicated net of meshes continuing into strong 

 spines, arranged tolerably in longitudinal series (PI. XIII. Fig. 12). In smaller pedicellariæ the net of 

 meshes is more slightly developed, and only quite few teeth or none at all are found (PI. XIV. Figs. 2, 

 6). The quite small ones have only an indication of a net of meshes above the apophysis, and their 

 blade is much narrower. As all transitions are found between these forms, no distinction can be made 



