NO. 1561. NEW UNSTALKED CRINOIDS— CLARK. 129 



ee. First pinnule not flattened on outer side; cirri in 10 vertical rows. 



/. 20 cirri ; calyx and arm bases smooth A. latipinna. « 



ff. 30 cirri; calyx and arm bases spiny (11 ) A. pubescens. 



lib. Less than 30 cirrus joints, without dorsal si)ines. 



c. Pinnules of eighth and following l)rachials have broad lower joints and 

 strong plates covering the genital glands. 

 d. Third and fourth joints of genital pinnules broad and nearly flat on the 

 outer side, but the fifth joint smaller. 

 e. First radials visible; arm bases smooth; 7-10 cirrus joints. 



(12) .1. liepburninna. 

 dd. Lower joints of genital pinnules uniformly expanded. 

 e. First radials concealed; less than 20 cirrus joints. 

 /. Calyx and arm bases rugose; first pinnule flagellate, with 40 or more 



joints (13) .4. kitn. 



ff. Rays separated laterally; radials scale-like, with a thin marginal 



flange; second radial hemispherical (14) A. scalar is. 



cc. Pinnules of tenth and following brachials have the lower joints as long as 

 or longer than wide, with no extensive plating over the genital glands. 



d. Basals prominent; radials long, not carinate. (15) A. r/arrettiana.f> 



dd. Basals, first radials, and often more or less of the second radials con- 

 cealed; (drri stout and rounded basally, slender and compressed 



distally ( 16 ) .1. orkm. 



aa. Pinnule ambulacra not plated. 



b. Three radials visible; stoutest piimnle on second lirachial; 30-40 rather 



elongate cirrus joints (17) A. minor. 



D. Bidistichate species with the radial axillaries and some of the following joints 

 more or less wall-sided, and a well-marked ambulacral skeleton on the pin- 

 nules [Spinifera group] . 



a. Over 30 cirrus joints, the later ones spiny. 



b. The first pinnule much smaller than the second; less than 20 cirri in five 

 well-separated double rows; arms long and slender, with more than 100 



joints; cirri long and rather stout, with about 80 joints ( 7 ) .1. anthus. 



bb. The first pinnule about the same length aa, or only slightly shorter than, the 

 second; cirri longer than the arms, stout, with about 110 joints. 



(8) A. macropoda. 

 bbb. The first pinnule as long as or longer than the second; cirri shorter than 

 the arms, 

 c. Centro-dorsal conical or shortly columnar, with 5 double rows of cirrus 

 sockets. 

 (/. 20 arms of sharply carinate joints. 



('. 70-90 slender cirrus joints .1. quinquecostatu. " 



ee. 50-55 stout cirrus joints (18) .1. diadenui. 



dd. 20 arms of rounded joints; radials not carinate; surface of radials and 

 lower brachials smooth; first pinnule not much stouter than succeed- 

 ing; 35-40 cirrus joints (19) A. asfer. 



ddd. Less than 15 arms of rounded joints; radials not carinate; surface of 

 radials and lower brachials covereil with spines; first pinnule nuich 

 larger and stouter than the succeeding; 50 cirrus joints. 



(10) A. rillusa. 



dddd. Less than 15 arms of rounded joints, but radials strongly carinate; 30 



cirrus joints (20) A. albojlava. 



"Inserted for comparison. 

 '' Also a l)idistichate species; see p. 130. 

 Proc. N. M. vol. xxxiii— 07 9 



