rto.1149. NOTES OK CYTHEREA CRASSATELLOIDES— STEARNS. 373 



an{?le darker, generally with Tiuiuerons close set linear rays of purplish 

 brown or brownish i)urple. The rays otherwise usually reddish brown 

 dark or ])ale, narrow at the umbones and gradually widening toward the 

 ventral margin. Tliese rays may be few in number on one valve and 

 numerous on the other; they often exhibit a somewhat serial arrange- 

 ment; again in some individuals the rays on both valves may be few 

 aiul narrow, linear; in other examples so numerous as to modify by 

 obscuring the ordinary lighter ground tint. 



The umbonal region is usually much lighter in these ("cream-color"); 

 sometimes, rarely, the tip of the umbos is white or nearly white, and 

 just below a tint of ])ale sienna-yellow. 



The incremental growth is often marked by broad or narrow zones of 

 purple. 



The large adults seldom show the various color features or markings 

 that are so often seen in shells one-third or one-half the maximum 

 size. 



The varietal segregation of such individuals as come within this 

 group is no doubt somewhat arbitrary. Nevertheless, following after 

 the type, we have certain facies that are reasonably separable when a 

 large number of shells from different localities are compared, and the 

 selections thus made by me for the U. S. National Museum series, 

 whether the same may be regarded as worthy ol" varietal distinction 

 or not, may be described as below : 



The number of rays in the type, as (igured in Keeve, is twenty, four 

 of them being on the posterior slope; six of the rays are broad, the 

 rest narrow, and three of the latter do not reach the beaks of the shell. 

 This Is in a general way a fair description of the average of the rayed 

 individual. 



The varieties following exhibit either very few, many less than the 

 average or veri/ many more rays than usual, giving at a glance a dis- 

 tinctive aspect to the examples included in these segregations. 



Variety a, pauciradiata. 



Light cream ground, rays reddish brown, few, linear, and usually 

 narrow. 



Variety /i, multiradiata. 



Ground tone very pale rufous, often slightly tinted with pale purple; 

 rays reddish brown, numerous, linear, narrow ; entire surface of valves 

 closely rayed ; rare. 



Variety y, alternata. 



Ground color pale brownish or rufous, with more or less narrow rays 

 irregularly alternating with broader rays; rays reddish brown. 



Variety d, eccentrica. 



Ground and rays the same color as in the foregoing; the number of 

 the rays on the two valves of the same shell conspicuously unlike ; often 



