68 TH. MORTENSEN, (Schwed. Südpolar-Exp. 



Classen u. Ordnungen. Echinodermen. IV. Die Seeigel 1904, p. 1390) makes both 

 Tripylus and Abatits synonyms of Honiaster. 



Though I cannot agree with Ag.\Ssiz in the diagnosis given b_\- him for the 

 genus Tripylus, I agree with him in regarding the species excavatiis as the type of 

 a separate genus, Tripylus. based on the following characters: The anterior lateral 

 ambulacra are not petaloid in their whole length from the ape.x down to the peri- 

 petalous fascicle; the 3 — 5 lower plates have only simple pores, a feature reminding 

 one, in fact, somewhat of Agassizia and not found in any of the other South Ame- 

 rican forms of the present group. The tubefeet of the odd ambulacrum are very 

 small and rather distant, with no distinct rosette plates and a quite rudimentar)- 

 sucking disk. These two characters, together with the well developed latero-anal 

 fasciole, evidently justif)- separating it from Abatus as a distinct genus, which, of 

 course, has to keep the name Tripylus I'lilL.; the name Hnuiaxitus TrosCHEL can 

 only be a synon}'m of Tripylus. All the other species, cavernosus etc., agree in 

 having no or only a rudimentary latero-anal fasciole (excepting the young ones); 

 the anterior lateral ambulacra are petaloid in their whole extent down to the peri- 

 petalous fasciole; the tubefeet of the frontal ambulacrum have a rather well devel- 

 oped sucking disk and rosette plates (least so in cordatus and Agassizii). These 

 species evidently make a natural group, for which the generic name ^(^i?/?« Trosch. 

 has to be retained. — In the pedicellaria- additional characters for distinguishing these 

 two genera are, apparently, not found. Both in Tripylus and Abatus we find a very 

 characteristic form of rostrate pedicellaricX- (PI XIX Figs. 30, 38), with the blade quite 

 open, almost flat, not widened in the point and generally very little bent. Globi- 

 ferous pedicellariœ have not been found in Tripylus: in Abatus they are of the 

 Scliizaster-tyi^t, with interior gland-room, and with 2 — 3 rather long teeth on either 

 side of the opening (seldom with only one tooth on either side). 



The species Tripylus Philippii Gray was removed to the genus Schizastcr, 

 nearest to S. fragilis. by Ag.\Ssiz in the : Revision of Echini» (p. 612) with there- 

 mark that, after it has been shown sthat the number of genital openings alone is 

 not a suitable generic distinction, and after LlTKEX's exhaustive comparison and 

 analysis of the reasons for uniting T. fragilis to Schizaster, there is no necessity for 

 further discussion of the question of the generic affinity of these two species. > * 

 I cannot at all agree with Agassiz here. As I have shown in the »Ingolf» Echi- 

 noidea II. p. 120—123, the species hitherto referred to the genus Schizaster form 



* It is not quite correct when it is stated in the »Revision of Echini» (p. 612) th.it Gray referred 

 his species to Trifyhis >on the same grounds which induced S.4RS to refer its northern congener to it>, 

 viz. the three genital pores. Gray does not give the number of the genital pores as a chief character of 

 the genus Tripulus, s.iying in the diagnosis of the genus »ovarial pores three or four» (Catalogue Rec. 

 Ech. p. 58). The char.icter upon which Gray distinguishes the genus Tripylus from Schizastt'r he expressly 

 says to be »the regular cordate form and central vertex» (Op. cit. p. 59). 



