266 Verrill, Notes 07i Madiata. 



the ordinary form, except that the color is light yellowish gray above, 

 with greenish radial shields and an niidefined greenish spot on each 

 upper arm-plate, the tips of the arms faintly handed with greenish ; 

 yellowish white beneath. Diameter of disk -17; length of arms '75 

 of an inch. 



Ophiactis simplex Lutken; Lyman, op. cit, p. 105. 



Ophiolepis simplex LeConte, Proc. Phil. Acad., v. p. 318, 1851. 

 f 0. 'Orstedii Latken.Vidensk. Meddelelser, 1856'; Addit. Ad. Hist. Oph., p. 129. 



Eight specimens of this species occurred with the last, from Panama. 



The species may be distinguished by the small, widely separated 

 radial shields ; rounded and regular disk-scales, with very few small 

 spines, except beneath, where they become more numerous; arms 

 longer and more slender than those of the preceding species; mouth- 

 papillse prominent and flat, one upon each side of the mouth-slits. 



The mouth-shields are transversely rhomboidal, with an angle within 

 and without. Five short arm-spines, of which the three middle ones, 

 are longest. Upper arm-plates broad-oval without a lobe. 



Color greenish, with lighter bands on the arms. 



In all our specimens there are six arms. They agree very nearly 

 with 0. Orstedii Ltltken,* which came from Puntarenas. 



Ophiactis arenosa Liitken, op. cit., 1856. 



There are a few young specimens, found with the last two species, 

 which appear to represent a third species. Whether they belong to 

 the present one or not is somewhat uncertain, owing to their imma- 

 turity. 



Mr. Lyman places this species as a doubtful synonym of 0. sim- 

 plex. Our specimens are insufficient to determine this question satis- 

 factorily. 



According to the original description by Dr. Liitken, its characters 

 are as follows : " 0. arenosa Ltitk. Mouth-shields roundish ; one 

 mouth-papilla^; upper arm-plates broad-oval; under arm-plates round- 

 ed, quadrangular, a little broader than long ; four short arm-spines, of 

 which the two middle are the longest. 



* Dr. Lotken's original description is as foUows: 0. Orstedii Liitk. Mouth-shields 

 broad rhomboidal ; one mouth-papilla ; five arms; upper arm-plates broad-oval; lower 

 arm-plates octagonal, a little broader than long; five short arm-spines, of which the 

 three middle and longest are only as long as one of the arm-joints. 



Color green, with bands upon the arms. 



Diameter of disk 4min. Length of arms 18™™. Puntarenas. 



