ECH1N0IDEA. II. IO y 



thodique. p 4 1 ), 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 Hemiaster (< )p. cit.i, I would not feel inclined to separate 



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



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



loppement de l'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 pedicellaria; have been found. The 



, , ., .. ,. . „ „-.,- _. , , , Fig. 21. Apical system of Periaster 



globiferous pedicellaria; (PI. XIV. Figs. 6, 9) have a rather large (glandular) limicola. h ,. 



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. — (July one small rostrate pedicellaria was found, which does not show any 



peculiar feature. The tridentate pedicellaria; occur in two, not very distinct forms: one (PL 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 meshwork in the bottom of the blade in these larger ones. 



In the largest specimen seen the valves are very unecpial 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 pedicellaria; 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 Agassi z in the Report of the * Blake - 

 Echiuoidea (Bull. Mus. Comp. Zool. V. 1878. p. 193. PI. Ill), except in having 110 distinct anal fasciole. 

 On the other hand I have seen in the British Museum (3) specimens of Periaster limicola 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 pedicellaria; 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 pedicellaria; 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- 

 cellaria; to be epiite true: they 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: .There must have been 

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



14* 



