8 BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



to corresponding plate or plates of the adjacent ray, or if rays are less than 10, the 

 joined pair of first marginal plates may be more or less interpolated between the 

 distal ends of the first adambulacrals. But the first adambulacral plates of adjacent 

 rays are never separated to their proximal ends, so that the mouth plates form the 

 apex of the interradial angle as in Brisingella. No matter what the number of rays 

 may be, the first pair of marginal plates is closely apposed for the whole length of 

 the plate, and, as stated above, their lower sides may be squeezed in between the 

 outer ends of the first or interradial pair of adambulacral plates. When there are 

 fewer than 10 rays these plates descend and separate the outer ends of the normally 

 united pair of adambulacrals in such a way that the marginals can be seen from 

 below. This seems to be a means of strengthening the actinostomial ring. A non- 

 muscular symphysis or syzygy between the first and second adambulacral plates, 

 and between the dorsal end of the second and third ambulacral ossicles. Adam- 

 bulacral plates short, with a crowded, characteristic armature consisting of an aboral, 

 obliquely transverse series of two subambulacral spines and one or two furrow spine- 

 lets, and usually also one adoral spinelet. The lateral spines and the major adam- 

 bulacral spines are typically long and bristling. Mouth plates small, with one to 

 three suboral spines. 



Remarks. — This genus is not so sharply differentiated as Brisingella and Steg- 

 nobrisinga, but is readily to be recognized by the crowded adambulacral armature 

 and the curiously modified, capitate, proximal subambulacral spines, which are 

 similar to those of Brisingaster de Loriol. 



The species to be included in this group are: Craterobrisinga panopla (Fisher), 

 0. parallela (Kcehler), C. alberti (Fisher), C. cricophora (Sladen), 0. eucoryne Fisher, 

 C. analoga Fisher, 0. variispina (Ludwig), C. multicostata (Verrill), and probably 

 also the aberrant C. evermanni (Fisher). In this species the proximal subambulacral 

 spines are longer and slenderer than is usual in Craterobrisinga, and the modified tip 

 is not so heavy as in typical species, nor is the adambulacral armature so crowded. 

 The second subambulacral spine is frequently quite small and easily mistaken for 

 an aboral furrow spinelet, but on certain plates, without any regularity that I can 

 discover, this inner subambulacral becomes nearly as large as the outer. On such 

 plates there is usually also an aboral furrow spinelet, making three in an oblique 

 transverse series, with the lateral spine additional, if such happens to be present. 

 These enlarged inner subambulacral spines are present on the outer part of the costal 

 region and beyond, and are not shown in the figures of the adambulacral plates given 

 by me in connection with the original description. (Fisher, 1906, pi. 48, figs. 2, 2a.) 

 In these figures only the dwarfed inner subambulacral spines are shown. The adoral 

 spinelet appears never to be present. 



CRATEROBRISINGA SYNAPTOMA Fisher 



Plate 1; Plate 6; Plate 7, Figure 3; Plate 12, Figure 3 

 Craterobrisinga synaptoma Fisher, Ann. and Mag. Nat. Hist., ser. 8, vol. 20, 1917, p. 426. 

 Diagnosis. — Rays 12, 14, and 15, with very long genital area crossed by 35 to 40 

 irregular, fairly well-spaced, complete and incomplete prominent spiniferous costae; 

 genital region equal to about 8.5 to 10 r, or 0.6 total length of ray; disk with promi- 

 nent spinelets, solitary except on primary radial plates, about 1 mm. long; no disk 



