42 BULLETIN- 82, UNITED STATES NATIONAL MUSEUM VOLDME 1 



established, there have been fitted into them new genera and species which have tended 

 to brid.ijo the gaps between. For instance the zenometrin genera with cirrus sockets 

 in cohinins in tlie radial areas separated by interradial spaces, such as Zenometra, 

 Sara?nctra and Psathyrometra, are linked with the Bathymetrinae by genera such as 

 Leptometra and Eumorphometra in which there are no interradial bare spaces on the 

 centrodorsal and the columns may even (particularly midradially) be somewhat irregu- 

 lar. Also some species of subfamilies other than the Zenometrinae may have the sockets 

 in quite distinct vertical rows, notably in the Helioraetrinae. As for the proportions 

 of tile distal segments of Pi, specimens of Thysanometra have now been described in 

 which these are distinctly longer than broad, contrarj- to the key. 



KEY TO THE SUBFAMILIES OF ANTEDONIDAE 



[Modified by A.M.C.; see above] 



a'. Cirrus soclcets arranged in definite columns on a conical or columnar, usualh' large, centrodorsal. 



Zenometrinae (p. 491) 



a*. Cirrus sockets arranged in transverse alternating rows, or irregularly, on a hemispherical to 



discoidal or conical centrodorsal. 



6'. Pi is composed of numerous (usually more than 50 and never less than 30) short segments of 



which at least the first 6 or 7, and usuaUy nearly all, are broader than long, and the distal 



are rarely more than twice as long as broad. 



c'. Cirri strong and curving, sometimes with dorsal processes on the distal segments. 



rf'. Cirri large, the peripheral ones with more than 25 segments Heliomethinab (p. 285) 



(P. Cirri short, with less than 20 segments Antedoninae (part)* (p. 43) 



c". Cirri weak and more or less straight Thtsanombtrinae (p. 266) 



6'. Pi rarely with more than 30 segments, often less than 20, and except for the basal ones these are 

 mostly elongated, the distal ones several times as long as broad and the whole pinnule some- 

 what tapered. 



c". The distal cirrus segments are entirely without dorsal processes on their distal ends; the cirri 

 are usually (but not always) short, rarely with more than 20, never with more than 30, 



segments.. Antedoninae (p. 43) 



c'. The distal cirrus segments always have the distal dorsal edge prominent, with the median 

 portion more or less produced in the form of a dorsal spine, and the iniddorsal line more or 

 Kss strongly carinate. 

 d'. Segments of the genital pinnules not conspicuously expanded. 



e'. Pa resembles Pi, and always differs from the genital pinnules; P. is sometimes and Pi 



occasionally, absent Peromethinae (p. 457) 



c'. Pj resembles P3 and the succeeding pinnules, and often bears a more or less developed 



gonad; all of the lower pinnules are inv.ariably present Bathtmetrinae (p. 646) 



(P. Segments of the genital pinnules conspicuously expanded Isometrinae (p. 617) 



Ze.n'gmetrinae (see figs. 25-34): Centrodorsal conical or columnar, with the 

 cirrus sockets in vertical columns, sometimes with naked interradial spaces between the 

 columns; cirri long, usually stout and flexible distally, rarely with less than 20 segments, 

 sometimes with moderate dorsal projections on the distal segments; Pi and P2 usually 

 similar, with most of the 10 to 20 (rarely as many as 45 or as few as 4) segments longer 

 tlian broad, often ver}- elongate. 



Heliometrinae (see figs. 15-18): Centrodorsal hemispherical to conical, with 

 the cirrus sockets crowded u-regularly or sometimes with a tendency towards arrange- 

 ment in v ertical rows; cirri long and strong with 25 to 75 segments, usually with 



•This covers AnUdonblfUa and pHatut, also A nmmara occidentalit, which all have numerous, more or less short, segments in Pi. 



