I QÓ 



which are also further protected by a heavj ventra] plating; the terminal seven segments are 

 small and delicate. P is similar, j.5 mm. long with 1 1 segments of vvith the sixth-tenth 

 expanded to protecl the gonads 1' ; is 1 mm. long with 1.; segments of which the fifth- 

 ninth are expanded. 1' is 3 mm. long with 1 ments, none of which are expanded; the 



pinnule is small and moderately stout. Hie following pinnules graduallj increase in length, tl)': 

 distal pinnules being 5 mm. long with 1 1 er 1 2 iegments. 



2°d Suborder MACR< IPHREATA. 



I. Family Antedonedai Norman (emended). 



Key to the Subfamilies of the Family Antedonidae. 



a 1 Cirrus sockets arranged in definite columns on a conical or columnar, 



usually large, centrodorsal . . Zen ome tri nac 



a Cirrus sockets arranged in transverse alternating rows, or irregularly, 

 on a hemispherical to discoidal or conical centrodorsal 

 b l the segments of the genital pinnules are much expanded, forming 



a roof over the gonads Isometrin ae 



h the segments of the genital pinnules are not expanded 



c 1 P, is composed of numerous (usually more than 50 and never 

 less than 30) short segments of which at least the llrst six 

 or seven, and usually nearly all. are broader than long, and 

 the distal are rarely more than twice as long as broad; 1', is 



as, or lonsjer than, 1\ 

 d 1 pne or more of the following pinnules resembles Pj . . H el i o m etri n ae 

 d P and the following pinnules are composed of segments 



which, beyond the third or fourth, are much elongated. . Thysanometrinae 



c 2 P, is composed for the most part ol much elongated segment'-. 



thorn/h a few of the basal segments mav be short: the distal 



segments are at least twice as long as broad 



d 1 the distal cirrus segments are entirely without dorsal pro- 



cesses on their distal ends; the cirri are usually (but not 



always) short, rarely with more than 20, never with more 



than 30, segments Antedon in ae 



d the distal cirrus segments always have the 'listal dorsal edge 

 prominent, with the median portion more or less produced 

 in the form of a dorsal spine, and the middorsal line more 

 or less strongly carinate 



I' resembles P,. and always differs trom the genital 



pinnules; ]', is freguently, and 1', occasionally, absent . Perometrinae 



