35S SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 5° 



slightly wider than long in the basal half of the arms, becoming 

 elongate d is tally ; third and fourth brachials usually united by 

 syzygy; a second syzygy between the ninth and tenth, or thirteenth 

 and fourteenth (or at some intermediate point), and others distally 

 with 3 to 8 (usually 4) bifascial articulations intervening; lower 

 pinnules smooth, slender, regularly tapering, flattened exteriorly, 

 the segments longer than wide ; distal pinnules long, the first seg- 

 ment very short, the second rather stout and trapezoidal, the others 

 long-cylindrical ; the fourth (i. e., "third") brachial always, and the 

 second sometimes, lacks a pinnule. 



Color in life reddish purple and white in varying proportions. 



Type of the genus. — Antedon diomedece A. H. Clark, 1907. 



Perometra is only known from the Philippine Islands and south- 

 ern Japan. The two species belonging to the genus are : 



Perometra balanoides (P. H. Carpenter) Perometra diomedece (A. H. Clark) 



13. PTILOMETRA, gen. nov. 



Centro-dorsal conical, columnar, or thick-discoidal, the cirri 

 usually in ten definite vertical rows or in five well-separated double 

 rows, occasionally without definite arrangement; cirri very long, 

 rather slender, with 80 to 130 segments, few of which are longer 

 than wide, the distal bearing dorsal spines ; disk and ambulacra 

 plated, but sometimes the former nearly naked ; costals broad, united 

 by bifascial articulation, in apposition laterally and strongly "wall- 

 sided," not very convex, usually bluntly carinate ; ten to thirty arms ; 

 distichals and palmars (when present) two, united by bifascial artic- 

 ulation ; palmars only developed on outer side of rays ; arms rounded 

 at the base, but becoming narrow and compressed distally, where 

 the brachials develop overlapping spines ; brachials short-triangular 

 or short-quadrate, the last few terminal joints abruptly turned 

 inward between the distal pinnules, which reach for several milli- 

 meters beyond the end of the arms; first pinnule about half (rarely 

 more) as large as the following pinnules ; pinnules stout, stiff, 

 strongly prismatic (especially the lower), the first joint short, the 

 rest medium, but little longer than wide. 



Color purple, dull yellowish white, or mottled. 



Type of the genus. — Alecto macroncma J. Miiller, 1841. 



Ptilometra ranges from Australia northward to southern Japan. 

 I had at first isolated Alecto macronema, making it the type of Ptilo- 

 metra, and including the other species in the genus Asterometra 

 with Antedon macropoda as the type, but further study has led me 



