CLARK: AUSTRALIAN AND INDO-PACIFIC ECHINODERMS. 133 



ules extends out on the arm so that there is no line of division between the latter 

 and the disc. The large tubercles tend to form a single series on the upper surface 

 of each arm, becoming gradually smaller as they approach the second fork, beyond 

 which they are rarely found. There are about 4 on the basal segment of the arm and 

 about 5 on each of the branches before the first fork. The arms branch about 

 6 times, the first division being about 20 mm. from the disc ; the resulting 

 branches are sometimes equal and sometimes strikingly unequal. Beyond the 

 second or third fork, the brauchlets are very slender and are covered by alternating 

 paired half-circles of granules and glassy booklets, so commonly found in the As- 

 trophytidae. The oral surface of disc and arms is covered with small, roundish, 

 flat granules, most numerous on the mouth-angles and bases of the arms. The 

 tentacle pores are small and indistinct ; the first pair (not counting those between 

 the mouth-angles) are between the first and second arm-joints and have no pro- 

 tecting tentacle-scales. Each succeeding pore is more or less concealed by a 

 slight ridge on its adoral side, which carries 4 (rarely 3 or 5) short, slightly 

 curved, peg-like spines or scales. Each spine is somewhat flattened and is a trifle 

 widened at tlie tip where its margin divides into 3-5 little glassy spinelets. Each 

 mouth-angle carries deep in the mouth a cluster of about half a dozen flat, 

 pointed teeth, and along each side of the mouth-slit are 3-5 spiuiform oral papillae. 

 The genital slits are prominent, about 2 mm. long. The madrepore plate is single 

 and rather conspicuous, about 2 mm. across. The color (dry) is almost uniformly 

 ■whitish, becoming more yellowish about the mouth and on the under side of the arms. 

 In a young individual (fig. 3), with the disc 8 mm. across, each radiating wedge 

 carries only a single conical tubercle. The .tubercles on the arms are arranged in 

 an almost perfect, single series. All of the tubercles are furrowed and ridged over 

 their entire surface. The arms branch only 3 or 4 times. The color is very light 

 brownish, darkest underneath. 



Of this remarkable species the M. C. Z. collection contains three dry specimens. 

 One of these (fig. 3) has been in the collection for many years and bears only the 

 label " Astrophyton australe ? Young " ; there is no indication of locality. The 

 other two were received in exchange from the Australian Museum and are 

 labelled, " Gorgonocephalus australis Verril ??? Off" Port Jackson, 40-50 fms." 

 The character of the disc shows that these specimens are not Gorgonocephalus, 

 but in view of the branching arms it is not altogether strange that they have 

 been referred to that genus. Both of the specimens from Port Jackson were 

 closely embracing the branches of a sponge. 



ECHINOIDEA. 



CIDARIDAE. 



Porocidaris elegans. 



Porocidaris elegans A. Agassiz, 1879. Proc. Amer. Acad., 14, p. 198. 



A fine series of ten specimens of this species, from off Port Jackson, N. S. W. 

 250-800 fms., is in the Museum collection. They are remarkably uniform in 



