ASTEROIDEA 



Three of the specimens from St. 1660 are perhaps full grown, being the same size as 

 Koehler's type — namely, R 15 mm., r 9-10 mm. The rays are bent strongly ventralward. 

 Two specimens are carrying numerous young in the concavity adjacent to mouth (27 

 January 1936). Two other examples from this station having R about 10 mm. are 

 strongly folded, while another is simply convex. The three small examples from St. 190 

 (R 7 mm.) are not folded ventralwards ; the disk is simply convex, and in one case the 

 ray tips are curved upward. Except when brooding young the animal probably is 

 spread out in normal sea star fashion as Mortensen found to be the case with living 

 examples of Stegnaster inflatus (Hutton). When preserved this species usually is strongly 

 convex (Mortensen, 1925, p. 304, pi. 13, fig. 11). 



A few notes need to be added to Koehler's account. He does not mention the papulae. 

 These are difficult to see from the outside, being small and largely obscured by the 

 granules. From the coelomic side of the dorsal surface they may be observed to occupy 

 a radial petaloid area extending from centre of disk two-thirds the distance to end of ray. 

 In this area there are about 16 papulae widely and unequally spaced. Koehler has 

 described the thin overlapping plates, which lack the internal marginally directed 

 process or lobe characteristic of the thin abactinal plates of Anseropoda. The abactinal 

 granules, of which figures are given, are characteristically expanded at the base, the 

 whole structure resembling an elaborate holothurian "table". The slightly convex 

 summit is uniformly beset with very numerous sharp thorns. The subcircular base of 

 each spinelet is in contact with its neighbours and is, of course, immersed in the 

 "dermal" layer of the skin. The effect of these "tables" is to form a calcareous layer 

 over the plates proper. The spinelets in alcoholic specimens, on account of their mem- 

 branous covering, appear to be simply convex granules. 



The gonads have short thick lobes, and are attached to the dorsal wall a short distance 

 from the margin of interbrachium. In the case of one of the specimens carrying young 

 the oviduct could be traced to the margin but the pore could not be located. 



There is a very short stout calcareous interbrachial pillar proceeding upward from 

 each mouth angle to the abactinal wall, the point of contact being less than k from 

 centre. The space between pillar and margin is devoid of a membranous septum. 



There are two brooding females. One of these has 26 young in a cavity involving the 

 proximal 5 or 6 adambulacral plates of each ray. These young are 4 mm. in diameter 

 and have about the same proportions as the adult, but the inferomarginal plates, 

 relatively more prominent than in the adult, carry 2 or 3 outstanding spinelets the series 

 of which forms a conspicuous fringe on the ambitus. As the animal grows and new 

 spinelets are added to the plate these original spinelets increase in thickness faster than 

 in length. In a specimen having R 6 mm. this marginal fringe of spinelets longer than 

 the others has disappeared. But in Mirastrella biradialis just the opposite has taken 

 place. The marginal fringe is accentuated as the animal grows. In these young there are 

 no actinal plates. There are 7 pairs of tube-feet. The first 4 or 5 adambulacral plates 

 carry a prominent inner spinelet and a small companion external and adoral to it; the 

 next I or 2 plates have only the inner spinelet. Each mouth-plate has 2 or 3 marginal 



