J^94 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



cellaria with jaws about twice as long as high. Each jaw is on a separate jjhite and 

 tlicy meet above tiie suture, being usually close to the furrow margin, and opposite 

 a suture between two adambulacrals. They are confined to the proximal third of 

 H, and are modifications of the ordinary ])ostadambulacral fascioles. In Ps. pec- 

 tinifer the spinelets of these are prominent and show a tendency to become flattened. 

 In dissonus the flattening is i)robably aided by a coalescence of spinelets, and the 

 result is a pedicellaria essentially like that of the tj'pical Goniasteridse, except for 

 the fact that the jaws stand on separate plates. The simplest postadambulacral 

 fascioles are thus incipient pedicellarise. The figures will, perhaps, show the exact 

 form better than further description. 



Combined mouth plates elliptical, slightly convex, broadest at about the 

 middle, and of the same general appearance as those of pectinifer. Besides the large 

 median unpaired blunt tooth are nine or ten slightly sharpened marginal spines. 

 The actinal surface is armed with numerous slender spinelets and one or two enlarged 

 spinules. (See description below of a smaller specimen.) 



Madreporic body small, situated 0.4 minor radius from center. Striations deep 

 and radiating. It is partly overhung by paxillse. 



Anatomical notes. — Superambiflacral plates well developed beyond eighth to 

 eleventh ambulacral ossicle. The first is on the fourth or fifth. The first plate 

 meeting an infcromarginal is on eighth to eleventh ambulacrals. The superambu- 

 lacrals are lodged in a sort of laminar septum, with an upper free edge, extending 

 between the ambulacral ossicles and the inferomarginals. In this low septum the 

 plate is firmly held. It is more in the form of a lamina than a rod. In the big 

 specimen, and to a less extent in the smaller ones, the superambulacral ossicles appear 

 to ])e jointed, probably due to artificial fractures partly healed, or possibly permanent, 

 owing to the unusual length of the plate. For instance, in the type as far along the 

 ray as there are two longitudinal series of intermediate plates these fractures occur, 

 and proximally there maj- be two in the length of a single plate. In Ps. pectinifer 

 the same tendency is observable, though not so marked. Over the distal region 

 with one row of actinal intermediate plates the superambulacrals are quite short, 

 and become rudimentary, then cease a short distance beyond the last intermediate 

 plate. Gonads in a single tuft on either side of interradial septum. Tube feet 

 with a prominent sucking disk; no deposits. Anus present. 



Notes on an immature specimen. — A specimen from station 3601 has been 

 referred to this species on the evidence of the peculiar pedicellarise, adambulacral 

 armature, and sui)erambulacral plates. Superficially it presents a number of points 

 of difference, which are probably due to age and the greater depth. 



R=52 mm.; r = 20 mm.; R = 2.6 r. Rays narrow dist ally. Paxillie conspic- 

 uously smaller on center of disk and on interradial areas than on radial areas; 

 the latter with ten or eleven central granules and twelve to fifteen smaller com- 

 pressed peripheral ones. Marginal plates not encroaching much on either area, 

 as in type, but the covering rather more granuliform. Adambulacral plates, as in 

 type — narrow, with a very prominent furrow angle; about six furrow spinelets, but 

 as few as three on a few proximal plates. Mouth plates prominent actinally, the 



