ECHINOIDEA. II. jq? 



thodicjuc. p4i), who liiuils the genus lu iiiciude only Uic species in wliicli tlie posterior ocular plates 



are not separated by the nuidreporite. Considcrini;-, however, what has been made known bv (i an thier 



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



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



a Tetude des Echinodermcs. VI. p. 175 and Lambert. Note snr le deve- 



loijpement de rEchiuospatagus iieocomiensis. p. 11. Note). The labruni 



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 papilke occur. Globiferous 



tridentate, rostrate and triphyllous pedicellariie have been found. The 



Fig. 21. Apical system of /V/'/Vm/c/' 



globiferous pedicellarue (PI. XIV. Figs. 6, 9) have a rather large (glandular) timicola. 'i,. 



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 pedicellarite 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. XI\'. 

 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 speciuiens (up to 2""" length of head) the serrations 

 are coarse and irregular; there is a little meshwork in the bottom of the blade in the.se larger ones. 

 In the largest specimen seen the valves are very unequal in length (PI. XIV. P'ig. 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 pedicellarice are of the usual form. 



The information given here is based on a specimen from the U. vS. 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 vBlakes- 

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

 On the other hand I have seen in the British Museum (3) specimens of iPcriastcr Umicola, from the 

 station («Blake St. 49) from which the species was first described; but these specimens differ so con- 

 siderabl}' in regard to the structure of the pedicellarice from what is made known above, that it 

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

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

 of these specimens in the Briti.sh Museum has proved this conclusion from the structure of the pedi- 

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

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



In the < Panamic Deep-Sea Echini > p. 210 Professor Agassiz says: vThere must have been 

 some mistake in the identification of the Schizasterid collected by the iChalleuger. (PI. XXX\'. b. 



14' 



