ECHINOIDEA. II. 



thodique. p 41), who limits the genus to include only the species in which the posterior ocular plates 

 are not separated by the madreporite. Considering, however, what has been. made known by Gauthier 

 about the apical system in some species of Hcmiaster (Op. cit), I would not feel inclined to separate 

 the P. limicola from the genus Periaster on this account (Comp. also De Loriol. Notes pour servir 

 a 1'etude des Echinodermes. VI. p. 175 and Lambert. Note sur le deve- 

 loppement de 1'Echinospatagus neocomiensis. p. n. Note). The labrum 

 reaches the beginning of the second adjoining ambulacral plates. The 

 actinal plates of the posterior ambulacra are rather elongate ; the first of 

 the 5 large subanal tube-feet is found on the 5th ambulacral plate. The 

 frontal tube-feet have a well developed disk, with numerous elongated, 

 narrow rosette-plates; the edge of the disk is not lobed. The spicules are 

 irregular, slightly branched rods. Long genital papillae occur. Globiferous 



tridentate, rostrate and triphyllous pedicellarise have been found. The 



Fig. 21. Apical system of Periaster 

 globiferous pedicellarise (PI. XIV. Figs. 6, 9) have a rather large (glandular) limicola. M/,. 



space within the blade, continuing almost to the articular surface; the 



terminal opening has two teeth on either side. The stalk has a thickening above and below, but no 

 free, projecting rods. - - Only one small rostrate pedicellaria was found, which does not show any 

 peculiar feature. The tridentate pedicellarise occur in two, not very distinct forms: one (PI. XIV. 

 Fig. 35) with the blade somewhat widened in about the outer third part, where the valves join, the 

 edge of this widened part being finely serrate, that of the lower part smooth; the other (PI. XIV. 

 Figs. 28, 44, 47) with the blade very elongated, slender, narrowing evenly towards the basal part, the 

 edge being serrate in its whole length. In larger specimens (up to 2 mm length of head) the serrations 

 are coarse and irregular; there is a little mesh work in the bottom of the blade in these larger ones. 

 In the largest specimen seen the valves are very unequal in length (PI. XIV. Fig. 47). This is probably 

 an abnormal case. The neck is well developed, the stalk has only a slight indication of a ring below. 

 The triphyllous pedicellariae are of the usual form. 



The information given here is based on a specimen from the U. S. Nat. Museum, which Pro- 

 fessor Rathbun has kindly sent me (Albatross St 2401. -- Gulf of Mexico. 142 fathoms). It agrees 

 closely with the description and figures of P. limicola given by Agassiz in the Report of the Blake- 

 Echinoidea (Bull. Mus. Comp. Zool. V. 1878. p. 193. PI. Ill), except in having no distinct anal fascicle. 

 On the other hand I have seen in the British Museum (3) specimens of <.<Pcriastcr limicola^ from the 

 station (Blake 81.49) fr lia which the species was first described; but these specimens differ so con- 

 siderably in regard to the structure of the pedicellarise from what is made known above, that it 

 seemed to me certain that it must be another species, viz. the Brissopsis alta Mrtsn. described below; 

 the pedicellarise of this latter species exactly agree with the present form. A renewed examination 

 of these specimens in the British Museum has proved this conclusion from the structure of the pedi- 

 cellarise to be quite true: they are very typical Brissopsis, with the subanal fascicle very well devel- 

 oped, quite agreeing in form and structure with the Br. alta described below. 



In the Panamic Deep-Sea Echini* p. 210 Professor Agassiz says: There must have been 

 some mistake in the identification of the Schizasterid collected by the Challenger (PI. XXXV. b. 



14* 



