304 PRor. P. M. dtjncan's eetisioit of the 



Adetes, the genera with suhanal fascicles are Prymnodesmia, and those 

 without them and with other fascicles are Prymnadetes (Loven). 



Spines vary greatly in dimensions, and in the shape and nature of the trans- 

 verse section ; may be hollow or more or less solid and reticulate 

 centrally; externally with close or distant wedges, or a merely solid 

 circmnference. They consist of a shaft variously ornamented, of a base 

 which is hollowed for the condyle or cup part of the joint for the reception 

 of the ball or mamelon of the articulating tubercle. The base may be 

 plain, or it may be crenulate, and will then correspond with a crenulation 

 on the ridt^e surrounding the base of the mamelon. The crenulation varies 

 in amount, and it may be present in some and absent in other tubercles 

 and spines upon the same test. The opposed crenulated surfaces give 

 attachment to the dense capsule of the joint, and there are no muscular 

 fibres in connection with them. Above the base of the spine, is usually, 

 but not invariably, a more or less symmetrical collar, which projects 

 beyond the shaft, and is sloped upwards to the shaft and ornamented with 

 the striations or grooves and ridges of the spine. The muscular fibres 

 which move the spine are inserted just below the collar, or upon the whole 

 of the underpart of it, and they arise from the edge of the scrobicule close 

 to the scrobicular circle of granules or tubercles, and may form a sheath. 

 Some spines are fixed, and arise at once from the test, as in Podocidaris. 

 (For general and especial structure see A. Agassiz, ' Eevision,' and Eeports 

 on the ' Challenger ' and ' Blake ' Echini ; Mackintosh, Trans. Eoy. Irish 

 Acad. 1878.) 



PedicellaricB have a short or long calcareous stem articulated upon granules, 

 and a short or very long flexible and soft part upon which is the bead, 

 formed by either two or by three valves. The stem may be glandular or 

 not, and glands exist in many instances within the head, also muscular 

 fibres and nerves. Pedicellarise have been classified under three terms, and 

 O. F. Miiller, 1788, Zool. Dan. vol. i. p. 16, called them P. globifera, P. tri- 

 •phylla, and P. tridens. The first have a spherical head and no neck, the 

 second have a bilobate short head and a produced neck, and the third have 

 a bilobate long head often with slender valves and a neck. These terms are 

 quite as useful as the more modern equivalents — P. gemmifonna, P. ophio- 

 cephala, and P. tridactyla. The " Globifera " of Hamann are large tri- 

 partite glands without an internal calcareous support. 



The figures of PediceUari^ in the Zool. Danica, vol. i. pi. xvi., ' Eevision 

 of the Echini,' and in the Eeports upon the ' Challenger ' and ' Elake ' 

 Echini, by A. Agassiz, should be studied ; also Valentin, 1841, Anat. Gen. 

 Echinus, in Agassiz, Monogr. d'Ech. viv. et foss. ; Sladen, 1880, Ann. & 

 Mag. Nat. Hist. ser. 6, vi. p. 102; Hamann, 1886, Sonder-Abdruek aus 

 den Sitzungsb. d. Jenaisch. Gesellsch. f. Med. u. Naturw. See also remai'ks 

 by Doderlein, 1885, Archiv f. Naturg. (Wiegm.), i. p. 82. 



