4 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



arising from the IIBr series. This, again, connects these genera with the group of 

 which Colobometra and Cyllometra are members. Furthermore, the general aspect of 

 Basilometra, especially of its pinnules and arms, is much like that of Colobometra, while 

 Epimetra reminds us equally strongly of Cyllometra. The general aspect of Ponti- 

 ometra also is not essentially different from that of Cyllometra, in spite of its great size, 

 the very large number of arms, and the very long cirri. 



The genus Cenometra represents a somewhat isolated type. The highly developed 

 and conspicuous ventrolateral processes on the ossicles of the division series and first 

 two brachials recall the similar processes in the species of Stephanometra; comparable, 

 but much smaller, ventrolateral processes occur in Basilometra. The greatly enlarged 

 and curved P 2 is suggestive of the proximal pinnules in Himerometra, and also in 

 Cotylometra and in some species of Iconometra. The cirri of Cenometra, with their very 

 short segments and paired dorsal processes throughout, are perhaps the most typical 

 of any in the family; but an approach to them is seen in certain species of Decametra. 



The genus Cotylometra also represents an isolated type, though obviously related 

 to the group including Oligometrides, and also to the group including Oligometra. Its 

 curious short and stout proximal pinnules and long cirri composed of segments most 

 of which bear a single large dorsal spine are quite unique. 



The genera Austrometra, Gislenometra, Analcidometra, Iconometra, and Oligo- 

 metrides are rather sharply differentiated from the other genera in the family by their 

 stout, stiffened, evenly and rapidly tapering and smooth proximal pinnules, including 

 PI, and appear by themselves to form a definite group. Austrometra from south- 

 eastern Australia, Gislenometra from southeastern Africa, and Analcidometra from 

 the Caribbean Sea and adjacent waters have the third-fifth segments of the genital 

 pinnules markedly broadened to protect the gonads, and include only very small 

 species; they seem to be more closely related to each other than either is to any other 

 genus. A slight broadening of the third-fifth segments of the genital pinnules is 

 sometimes to be seen in some of the species of Iconometra, for instance in /. japonica, 

 to which they may be assumed to be more distantly related. 



Iconometra is obviously closely allied to Oligometrides, having the same type of 

 proximal pinnules in all the included species, and the same proximal transverse ridge 

 on the cirrus segments in all the species except /. japonica in which the transverse 

 ridge is at first distal, later becoming median, as in Oligometra. Iconometra repre- 

 sents a sort of generalized type closely approaching Oligometrides, with a single species 

 approaching Oligometra in its cirri and suggesting Austrometra and Analcidomelra in 

 its genital pinnules. Iconometra, occurring from southern Japan to Torres Strait and 

 westward to Flores, has a more restricted range than Oligometra, though it has a 

 much broader range than the other four genera of the group Oligometrides, Austro- 

 metra, Gislenometra, and Analcidometra. It should be noted that Iconometra is the 

 only genus in this group including species with more than 10 arms. 



The largest group in the family includes the genera Petasometra, Cyllometra, 

 Decametra, Colobometra, Alisometra, and Oligometra. Typical, or rather extreme, 

 species of these genera, as Petasometra helianthoides, Cyllometra manca, Decametra 

 mylitta, Colobometra perspinosa, Alisometra owstoni, and Oligometra carpenteri, are 

 very different, but each of these genera includes more or less generalized species that 



