266 VERRILL 



these were dark purple, but some were orange. Among them were 

 two six-rayed specimens and one very large one with seven perfectly 

 regular rays. Fisher records it from many localities, mostly off the 

 California coast, from low tide to 165 fathoms, and also from the 

 Gulf of California, north of La Paz, in 33 fathoms. 



VARIATIONS. 



Many regular six-rayed examples occur of full size. From Pacific 

 Grove (coll. Prof. W. R. Coe), there is also a four-rayed specimen 

 which is quite regular, except that one ray has been broken off and 

 not fully restored. A regular seven-rayed specimen has been 

 received from Vancouver Island (pi. cviii, fig. i), Canadian Geologi- 

 cal Survey. Its radii measure 58 mm. and 84 mm. With the latter 

 was a regular six-rayed specimen, with the radii 48 mm. and 72 mm. 



Suborder VELATA Perrier. (See p. 204.) 



Family PTERASTERIDM Perrier. 



PterasteridcB Perrier, op. cit., 1875. 



Pterasteridce (pars) Sladen, Voy. Challenger, vol. xxx, p. xxxvii, p. 468, 1889. 

 Fisher, op. cit, igiib, p. 343. 



This is one of the most peculiar groups of starfishes hitherto dis- 

 covered. It shows, in general characters, a remarkably high degree 

 of specialization not found in any other group. Most of the genera 

 and species are from the deep sea. 



Disk usually plump ; rays five to eight, rarely nine ; upper surface 

 covered by a supradorsal membrane, supported by the tips of long, 

 slender, divergent, often webbed, paxillary spinules and pierced by 

 small concentric pores or " spiracles," often closed and invisible in 

 preserved specimens, and usually with a larger central osculum. 

 Beneath this membrane is a " nidamental " cavity or gonocodium, 

 traversed by the columnar pseudopaxillae, and containing the 

 papulae, which are often branched. In this cavity the eggs are 

 retained, and also the young, till they assume the adult form and 

 considerable size. 



The dorsal skeletal ossicles are lobed or cruciform, loosely reticu- 

 lated. The adambulacral spines usually form transverse webbed 

 combs or fans ; not webbed in Hymenasterinse. Series of slender, 

 divergent spines, more or less appressed, and attached to the under 

 surface, or imbedded in it, and usually webbed to the adambulacral 

 fans in Pterasterinse, are always present. These peculiar spines, 

 called " actino-lateral spines " by Sladen, should rather be called 



