ECHINOIDEA. II. 



107 



thodique. P4i), wlio limits tlie genus to include oiily tlie species in which the posterior ocular piates 

 are not separated by tlie niadreporite. Considering, however, what has been made known b\- Gauthier 

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

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

 å l'étude des Echinodermes. VI. p. 175 and Lambert. Note sur le déve- 



lopijement de rEchinospatagus neocomiensis. p. 11. Note). The labruni / > 



reaches the beginning of the second adjoining ambulacral piates. The i X /^| | \ 



actinal piates of the posterior ambulacra are rather elongate; the first of ) /'^^^.^ /^ ■."•■• '3— -.!\ 

 the 5 large subanal tube-feet is found on the 5th ambulacral plate. The T ^^^k / ■•'' '''/«^^^ \ 

 frontal tube-feet have a well developed disk, with numerous elongated, I ^^^F/ ■•'•'.' A^^^ / 



narrow rosette-plates; the edge of the disk is not lobed. The spicules are \ J '''■".' '. '\ / 



irregular, slightly branched rods. Long genital papillæ occur. Globiferous / . X/ ' " jTj 



tridentate, rostrate and triphyllous pedicellariæ have been found. The ^~~^ ^^-^vr"^ 



Fig. 21. Apical system of Pcriaster 



globiferous pedicellariæ (PI. XIV. Figs. 6, 9) have a rather large (glandular) ihnicola. 'i/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 pedicellariæ occur in two, not very distinct forms: one (PL XIV. 

 Fig. 35I 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""" length of head) the serrations 

 are coarse and irregular; there is a little meshwork 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 abnornial case. The neck is well developed, the stalk has only a slight indication of a ring below. 

 The triphyllous pedicellariæ 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 (;<Albatrossv 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 ^Blako- 

 Echinoidea (Bull. Mus. Comp. Zool. V. 1878. p. 193. PI. III), e.xcept in having no distinct anal fasciole. 

 On the other hånd I have seen in the British Museum (3) specimens of -Pcriastcr liiiiicola from the 

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

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

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

 the pedicellariæ 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- 

 cellariæ to be quite true: they are very t^pical Brissopsis, with the subanal fasciole very well devel- 

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



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

 some mistake in the Identification of the Schizasterid collected by the «Challengerv (PL XXXV. b. 



14* 



