REPORT ON THE CR1NOIDEA. 220 



lateral flattening of the lower brachials is scarcely more distinct than in Antedon 

 jiagellata or Antedon brevicuneata ; but the first pinnule has prismatic lower joints, and 

 the ambulacra of the disk, arms, and pinnules are well plated, though the interpalmar 

 areas of the disk are comparatively bare. The genital pinnules are not specially 

 distinguished, however, except by their shortness, and their glands are not protected by 

 any special pavement of plates as in Antedon jlexilis and Antedon patula, though there 

 is an ambulacral skeleton above them which is less completely differentiated than in the 

 slender later pinnules. 



The presence of blunt spines on the later cirrus-joints also distinguishes this species 

 from the three just described, all of which have very smooth cirri (Pis. XLII., XLIIL; 

 PI. XLIV. fig. 1), and are altogether of a more robust nature. 



The two individuals which the Challenger collected at Station 192 are essentially 

 similar in all their characters ; but a younger specimen from Station 201 has much 

 smoother joints at the bases of the arms, their distal edges being but little raised ; while 

 in some fragments of a larger form obtained at the same locality there is a tendency to 

 expansion in the third and fourth joints of some of the genital pinnules, which recalls 

 their condition in Antedon Jlexilis (PI. XLII.). The interpalmar areas of the disk are 

 also more plated than in the examples from Station 192. 



7. The Palmata-gxovq). 



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. 



Remarks. — This group is not only extremety well-defined as regards its general 

 characters, but it is also distinctly limited in its distribution, both bathymetrical and 

 geographical. 



The disk is either naked or bears but a few isolated plates, and there is no definite 

 ambulacral skeleton. The ambulacra may be supported by isolated rods and networks 

 of limestone, but they never form distinct covering plates like those of the Basicurva- 

 and $pmi/era-groups. In a few species like Antedon jiagellata and Antedon similis 

 (PL XLVII. fig. 1), which have the rays closely approximated, the lower brachials of 

 their outer arms are somewhat flattened laterally. But this condition is not a constant 

 one, and it does not affect the lower pinnules ; so that it is altogether different from the 

 flattening of the arm-bases in Antedon basicurva, Antedon valida, or Antedon robusta 

 (fig. 3 on p. 122 ; PI. XV. fig. 6 ; PI. XLIV. fig. 1). 



We have seen that the Spinifeixt-growp among the bidistichate species corresponds 

 to the Basicurva-gvo'a'p of the ten-armed type ; and in like manner the ten-armed 

 Milberti-grouip is represented in the bidistichate series by the Palmata-gvouip, all the 



