66 



OPHIOZONA IMPRESSA. 



several smaller scales ; scales of interbrachial spaces below, smaller and 

 thinner than those above. Arm-spines five, short, moderately stout, 

 tapering, rounded, uppermost one shortest, two lowest ones rather the 

 stoutest ; lengths to that of under arm-plate (seventh joint), .6, .7, .7, 

 .9, .9:1; near end of arm, only three spines ; and even near its base, 

 there are often only four. Tentacle-scales two, stout, longer than broad, 

 set close to each other, and forming together an oval. Color, in alco- 

 hol : above, disk-scales and arm-plates vandyke-brown, some of them 

 edged or mottled with white ; arms irregularly banded with burnt 

 umber ; below, arms and mouth parts faint yellowish-brown ; interbra- 

 chial spaces nearly white, with a tinge of greenish. 



Variations. — The larger disk-scales are in some specimens more 

 prominent and distinct than in others ; occasionally there are only 

 three, instead of five, radiating rows of larger scales, in each interbra- 

 chial space above. The color, in alcohol, varies a little in intensity. 

 The projDortions of the arms to the disk may be as 9.2 : 36, 11 : 41, 

 12.5 : 66, 13.2 : 51, 14 : 57, or 15.5 : 64. 



O. impressa has been taken at St. Thomas, in from one to four feet 

 of water, on a sandy bottom, or on corals (A. H. Riise) ; also on the 

 coast of Florida (Professor Agassiz, Mr. Wurdeman). It may be dis- 

 tinguished from O. jKicifica by having longer arm-spines, which are not 

 of equal lengths. 



LIST OF SPECIMENS. 



