264 Verrlll, JVotes on Eadlata. 



Ophiactis Llitken. 



Of this genus there have been described four nominal species from 

 the Panamic Province, besides one from Peru. Of these, it is proba- 

 ble, as has been suggested by Mr. Lyman, that 0. Orstedii Ltitken, is 

 a synonym of 0. simplex (LeConte sp.), no differences yet indicated 

 being sufficient to separate them clearly. 



The species of Ophiactis may be recognized by their rather short 

 arms and stoiit disk, covered above with overlapping scales and 

 a few, small, scattered spines ; usually with separated radial shields. 

 There are commonly four to six rows of arm-spines, which are 

 rough, short, and stout, projecting at right angles from the arms. 

 There is but one tentacle-scale and but one or two mouth-papilla? on 

 each side of the mouth-slits. The species are mostly small and often 

 have six arms. 

 Ophiactis Kroyeri Llitken, Vidensk. Meddelelser, 1856; Lyman, op. cit., p. 108. 



Mr. Bradley has sent several hundred specimens of this species 

 from Callao, Peru, where they were found in abundance among the 

 interstices of JBalani, Discince, My till, etc., scraped from the bottom 

 of a vessel that had been a long time in that port. Some of the lar- 

 gest specimens have arms 1*7 inches long and the disk '35 in diameter. 

 Of this species I have seen no specimens having six arms. 



The color varies considerably, but most frequently is dull greenish, 

 in alcohol, with a few irregular bands of purplish brown upon the 

 arms ; beneath grayish or greenish white. Some specimens are pur- 

 plish brown above, with bands of greenish on the arms, and others 

 are yellowish gray, with or witliout bands of darker. Frequently the 

 upper arm-spines have a spot of white at base. The radial shields 

 ax'e usually darker green or brown than the rest of the disk, and have 

 a yellow spot on the outer end and are sometimes edged with white, or 

 have a white spot at the inner end. In other specimens the radial 

 shields are yellowish with a greenish disk. The disk may, also, be 

 mottled with lighter and darker. 



The number and size of the spines upon the disk are also quite vari 

 able. In some cases they are nearly or entirely absent, while in others 

 they are quite numerous, long and sharp, scattered all over the disk, 

 except on the large radial shields ; more frequently, however, they are 

 mostly confined to the interradial spaces of the disk, and are rather 

 few in number. The radial shields are large, acute-triangular, with the 

 point inward and a prominent, elevated lobe on the corner where 

 they join their neighbors ; the inner ends are separated by about four 

 plates, of which the outermost is very narrow and the mnermost 

 rounded. The mouth-shields are short and broad, with an elongated) 



