MONOGRAPH OF THE EXISTING CRINOIDS. 



41 



Carpenter did not subdivide the genera Antedon and Actinometra, but he 

 arranged the species in a number of more or less well defined groups for the better 

 appreciation of their differential specific characters (but not of their specific inter- 

 relationships), as follows: 



ANTEDON. 



Series I. The two outer radials united by Byzygy. (This includes only the 



"Elegans group"; Carpenter did not employ this name in the Challenger 



report, introducing it for the first time in his report on the comatulids of 



the Mergui Archipelago, 1889.) 

 Series II. The two outer radials articulated; 10 arms. 



The radials and lower brachials have flattened sides; pinnule ambulacra 

 generally plated 1. 



The rays not flattened laterally. Pinnule-ambulacra well plated 2. 



The first two or three pairs of pinnules long and flagellate, with numerous 

 short and wide joints 3. 



The joints of the lowest pinnules, which are often long and slender, are 

 longer than wide, frequently very much so 4. 



The first pair of pinnules is comparatively small, and their joints but 

 little longer than wide; one or more of the second, third, and fourth 

 pairs are longer and more massive, with stouter joints than their suc- 

 cessors 5. 



"Bnsicurva group." 

 "Acasla group." 



"Eschrichti group." 

 "Tenella group." 



" Milberti group." 



There are in addition six 10-armed species which Carpenter does not assign to 

 any of the preceding groups. 



Series III. Two articulated distichals. 



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 pinnules 6. "Spinifera group." 



Bidistichate species with an unplated disk and no definite ambulacral 

 skeleton. The sides of the lower brachials are scarcely, if at all, 



flattened. The first pinnule smaller than its successors 7. "Palmata group." 



Series IV. Three distichals, the first two articulated, the third axillary with a 



syzygy. 



Tridistichate species with plated ambulacra and the lower parts of the 



rays flattened laterally 8. "Granulifem group." 



Tridistichate species with an unplaled disk and no definite ambulacral 



skeleton; the bases of the rays are not flattened laterally 9. "Savignyi group." 



ACTINOMETEA. 



* 



Series I. The two outer radials and the two first brachials respectively united 

 by syzygy. 



Ten arms 1. "Solaris group." 



Two distichals, united by syzygy 2. "Paucicirra group." 



Three distichals, the axillary a syzygy 3. "Typica group." 



Series II. The two outer radials articulated; 10 arms 4. "Echinoptera group." 



Series III. Two articulated distichals. 



Two articulated distichals. The palmars and subsequent series, when 

 present, are of the same character; but the first two brachials are 



united by syzygy 5. "Stelligera group." 



Two articulated distichals; the first arm syzygy in the third brachial. ... 6. " Valida group." 

 7!H4G Bull. 82 I!) 4 



