2026. REVISION OF CRINOID GENUS HIMEROMETRA— CLARK. 285 



In Himerometra martensi and H. rolustipinna the proximal pin- 

 nules are essentially as in H. sol and H. magnipinna; but the speciali- 

 zation has been carried a step further by the suppression of the 

 flagellate tip, so that the pinniiles are reduced to stout curved horn- 

 like structures. //. martensi, m which the distal edges of the pumule 

 segments are prominently spinous, appears to be a step in advance 

 over H. rohustipinna. 



Of these three specific groups the most primitive (mcluding H. 

 persica and H. lartschi) has the greatest range, from the Persian Gulf 

 to the Philippines, the more specialized of the two species mhabitmg 

 the East Indies and the more generalized the Persian Gulf; the next 

 most prunitive (mcluding R. sol and H. magnipinna) has the next 

 greatest range, from the Maldive Islands to the Philippines and the 

 Admiralty Islands, and again the more specialized of the two species 

 mhabits the East Indian region and the more generalized the western 

 limit of the range of the group, the Maldive Islands; the most special- 

 ized (including H. martensi and H. rohustipinna) has the most re- 

 stricted range, occurrmg only as far to the westward as the Mergui 

 Archipelago, the more specialized of the two species being known 

 onl}^ from the Straits Settlements and North Borneo, while the more 

 generalized ranges from the Mergui Archipelago to the Moluccas and 

 the PhUippmes. 



KEY TO THE SPECIES OF THE GENUS HIMEROMETRA. 



a'. Enlarged proximal pinnules slender, flagellate distally, and very long (slightly 

 more than one half as long as the cirri), composed of from 36 to 40 perfectly 

 smooth segments most or all of which are longer than broad; a few of the earlier 

 segments are narrowly, but prominently, carinate; the earlier segments of the 

 following pinnules are very strongly carinate; the segments in the outer half 

 of the cirri have prominent dorsal spines. 

 ¥. 20-25 arms; about 35 cirrus segments; all of the segments in the proximal pinnules 



longer than broad (Persian Gulf) persica (6) 



6^. 35-55 arms; about 40 cirrus segments; a few of the basal segments in the proximal 



pinnules are broader than long (Philippine Islands) bartschi (5) 



a^. Enlarged proximal pinnules very stout, with all or nearly all of the component 

 segments broader than long, or at least as broad as long; none of the segments are 

 carinate; following pinnules without carinate processes on the earlier segment 

 ¥. Enlarged proximal pinnules with about 30 segments, very stout basally and dis- 

 tally gradually tapering to a delicate and flagellate tip; the distal edges of the 

 segments in the middle half or proximal two-thirds are swollen and may be 

 strongly everted, but are always smooth, never spinous. 

 c^. Cirri very stout, stouter than in any other species of the genus; the enlarged 

 proximal pinnules have the segments in the basal two-thirds with strongly 



produced and everted distal edges (Maldive Islands) sol (4) 



c^. Cirri rather short and weak without, or with only slight traces of, dorsal proc- 

 esses on the outer segments; the enlarged proximal pinnules have the seg- 

 ments in the middle half with slightly swollen distal edges (Cochin China, 

 Philippine and Admiralty Islands, and St. Mathias Island), viagnipinna (3) 

 b'~. Enlarged proximal pinnules with 20 or fewer segments, distally tapering more 

 or less abruptly and without a flagellate tip. 



