SHALLOW-WATER STARFISHES 93 



shorter row of similar synactinal spines, extending to the distal 

 third, intervenes between the peractinals and the adambulacrals, but 

 is separated from the latter by a definite channel, having papulae 

 proximally. Close to the base of the rays some of the infero- 

 marginal and actinal plates often bear two or three small extra 

 spines, and all bear dense clusters of minor pedicellariae on the outer 

 side. The adambulacral spines form a single very regular row; 

 they are slender, tapered, and subacute; about five correspond to a 

 single actinal spine. The adoral ones become somewhat longer. 

 Many of them bear thick clusters of forficulate pedicellariae of 

 various sizes in a single cluster. Between their bases and on the 

 inner edges of the ambulacral grooves, and on the oral spines, and 

 interradial areas are many large major pedicellariae, part of which 

 are unguiculate, like those of the back, but others are longer, com- 

 pressed, lanceolate, with the tips subacute, or terminating in one or 

 two hook-like teeth. The pedicels of these, and also of those 

 attached to the spines, are often surrounded by large clusters of 

 small forficulate pedicellariae of nearly the same form, but of various 

 sizes, many being as minute as the ordinary minor pedicellariae. 

 Friday Harbor, Puget Sound (Professor Kincaid). 



The paucity of spines on the back of the specimen above 

 described might be thought to be due in part to some injury and 

 lack of subsequent restoration of the spines. But on the distal part 

 of the rays, at least, the spines seem to be certainly normally 

 arranged. There are no naked ossicles or tubercles where spines 

 are likely to have been attached. 



I have examined four additional specimens (No. 1904, Mus. 

 Comp. Zool.) from the same district and also sent by Professor 

 Kincaid. They are all larger. One of them agrees closely with the 

 type specimen described above. Its radii are 1 10 mm, and 330 mm. 

 Others, equally large, have the disk and rays flattened in drying 

 and appear to have more numerous and larger spines and fewer 

 pedicellariae. One has the radii 85 mm. and 330 mm. 



This species is rather closely related to P. brevispinus (Stimpson). 

 But the characters of the dorsal spines and pedicellariae and of the 

 actinal spines, and the larger spines and papular areas, seem to 

 require their separation. Of course a much larger series of specimens 

 than I have studied might show intermediate forms, as in other cases. 

 The difference in the number of rows of actinal spines is greater than 

 we should expect in specimens of similar size. The dorsal spines 

 are much less numerous in our species and the rays much longer 



