ECHINOIDEA. I. 163 



With regard to the other synonyms and tlie imniense nnmber of piaces in the literatiire where 

 tilis species is mentioned or more thoronghly treated, the reader is referred to Rev. of Ech. and 

 Bell's Catalogue. — As it has been treated so man)- times, I shall only liere mention a few featnres 

 that have not before been described witli sufficient clearness. 



With regard to the provision of the test with tubercles very great variation is fonnd. On 

 PI. XVI. Figs. 17 and 23 is represented an anibulacral and an interambnlacral area of a specimen 

 with comparatively few tubercles (S ar s' s Sir. pallidns), Figs. 11 and 21 represent the same of a 

 specimen with numerous tubercles [graniUaris Say). The difference is here very conspicuous, and 

 nevertheless the represented forms are b\- no means extreme ones. All transitional forms between 

 these niay be found. The number of the pores varies between 4—7, but most commonh- 5 or 6 are 

 fonnd. Generally two ocular piates reach to the periproct (PI. XVI. Fig. q), sometimes three, more 

 rarely one. On PI. X\T. Fig. 4 is figured the apical area of a specimen with two pores in one of the 

 genital piates. 



The buccal niembrane contains rather numerous fenestrated piates some of which are large, 

 very complicated, and carry pedicellariæ; those inside of the buccal piates are, as usual, smaller 

 (PI. XVI. Fig. 13). Very few bihamate spicules in the buccal membrane and the gills, which latter 

 otherwise contain the usual irregular fenestrated piates. 



The pedicellariæ. It was the pedicellariæ of this species which were figured by O. F. Muller 

 in Zoologia danica; among the later authors only Per ri er') has studied them more thoronghly and 

 figured sonie of the skeletal parts. Also Agassiz gives some figures (Rev. of Ech. PI. X), but they 

 are too small to show the interesting features found here. — The globiferous pedicellariæ (PL XX. 

 Figs. 16, 25, 26, and 29) are highly characteristic and widely different from those of all the other Echi- 

 nids occurring in the northern Atlantic. The head is not, as in those, placed directly on the stalk, 

 but connected with it by a long, muscnlar neck, provided with as well longitudinal as circular muscles, 

 so that it may be stretched out and retracted, and the head nia\- be moved freely in all directions. 

 The blade is tubular, without lateral teeth, only with a more or less marked obliquity above. Per- 

 ri er' s figure (PI. V. Fig. 7. a) of sucli a vah'e is rather unfortunate, as it seems to show two end-teeth. 

 The form of the basal part is ratlier varying, as the outer corners may be more or less conspicuous 

 or bent .somewhat inward. Most frequently some spicules are found in the head, arranged in a narrow 

 band along the edge of the valves (Fig. 29). The stalk is a hollow tube peculiarly furrowed above. 

 (Also the stalks of the other pedicellariæ are hollow.) The globiferous pedicellariæ are generally 

 large and strong; they are sometimes found in so great numbers as to be almost more conspicuous 

 than the spines (on the abactinal side). Sometimes they are quite light, sometimes quite dark from 

 pigment; the more pigmented they are, the fewer spicules they seem to contain; they may also quite 

 waiit spicules. 



The tridentate pedicellariæ are of very different forms (PI. XX. Figs. 4, 6, 20); the blade may be 

 long and narrow, or short and broad, deep with almost adjoining edges, or flat and broad; uow there 

 is a strong mesh-work, now almost none. The ophicephalous and triphyllous pedicellariæ (PI. XX. 

 Figs. 3, 5) without marked peculiarities. — The spicules (PI. XX. Fig. 12) are branched at the ends, but 



I) Recherches sur les Pedicellaires. p. 152. 



