256 NEW STARFISHES AND OPHIVBANS—VEBRILL. vol.xvii. 



fishermen, taken on tlie fishing banks off Nova Scotia and Newfound- 

 land, in 84 to 230 fathoms. 



BATH YBIASTEK ROBUSTUS, V e r r i 1 1 . 



Archaster robustus, Verrill, Amer. Jouru. Science, xxix, p. 383, 1885. 

 Phoxaster piimilm, Sladen, op. cit., xxx, p. 236, pi. 15, tigs. 3-6; pi. 40, figs. 7-11, 

 1889 (Young). 



This species is evidently very closely related to B. pallidus, of North- 

 ern Europe, the type of the genus Bathyhiaster. It is even possible 

 that they may prove to be identical when a full series of each can be 

 compared. 



The form described as Phoxaster pumilus by Sladen, which was taken 

 off the North American coast, in 1,240 to 1,700 fathoms, appears to be 

 identical with the young of our species. His specimens were only 

 62 mm. in diameter. The genus Phoxaster in this case becomes a syno- 

 nym of Bathyhiaster. 



Fully grown examples of B. robustus are often 250 to 280 mm. in 

 diameter. 



In the young specimens, up to about 75 mm. in diameter, the cen- 

 tral ''epiproctal cone" is still visible as a low wart-like elevation, with 

 an aperture in the tip, but in the large specimens it disappears entirely 

 and the central area of the disk becomes flat, or even concave, and 

 covered with crowded i^axilliform plates much smaller than those on 

 the rays, but the small central pore is persistent. The peculiar purse- 

 like or bursiform pedicellarife of the large inner adambulacral spines, 

 characteristic of Bathyhiaster^ are often entirely wanting in our speci- 

 mens, especially when small, and usually, when present, there are but 

 few of them even in the large specimens. Possibly they may have 

 been destroyed by rough usage in the dredges and washing sieves. 

 The squamiform spinules and pedicellarine of the actinal and marginal 

 plates are like those of Bathyhiaster pallidus. The two rows of si)inules 

 on each jaw-plate are peculiar, for the opposite spines of each pair 

 press their tips together something like the valves of certain x>edi- 

 cellariae, but this seems to be the case in the European form also. 

 These spines are subequal in length — short, with flattened blunt tips; 

 those of the actinal series, in large specimens, are stoutest, often with 

 enlarged, truncate, bilobed, or rough ends; there maybe 15 to 20 in 

 each row. The two close parallel rows of spines on the first adambu- 

 lacral plates are similar in form and arrangement. Of these there 

 may be 10 to 12 in each row. The adambulacral plates, except the 

 first pair, correspond in number to the marginal plates. The actinal 

 interradial plates form short, simple rows running from each plate to 

 a corresponding marginal plate; their marginal scales form narrow 

 fascioles, which become more distinct and regular in the narrow, con- 

 tinuous vertical grooves between both series of marginal plates. Tbe 

 longitudinal sutures between the upper and lower plates are very 



