598 BULLETIN 159, UNITED STATES NATIONAL MUSEUM 



132. All 5 pairs of legs lacking; first antennae 1-segniented, bi- 



partite at tip, unarmed; second antennae and maxillipeds 

 lacking; 1 pair of maxillae; on an ophiurid. 



cf 9 Arthrochordeumiuin Stephensen, 1918 

 First 3 pairs of legs present and uniramose, the others lacking 133 



133. First and third legs 4-segmented, second pair 3-segmented, 



with an apical disk; genital segment produced laterally; 

 egg cases turned forward and out; on annelids. 



cf ? Selioides Levinsen, 1878 

 First and third legs 5-segmented, second pair 2-segmented, 

 with 2 apical spines; genital segment not produced; egg 

 cases lobed on their outer margin; on annelids 9 Selius Kr0yer, 1837 



KEY TO THE GENERA OF THE SUBORDER NOTODELPHYOIDA 



(The segmentation of the first 4 pairs of legs and the structure of the fifth 

 legs and second antennae furnish the best means of identification.) 



1. First 4 pairs of legs biramose, rami 3-segmented 2 



First 4 pairs of legs biramose, rami 2-segmented 15 



First 4 pairs of legs biramose, rami 1-segmented 18 



First 4 pairs of legs biramose, rami not uniformly segmented 29 



First 4 pairs of legs uniramose, some of them often lacking 37 



First legs biramose, 3 following pairs uniramose, rami 1-seg- 

 mented; fifth legs laminate, 1-segmented; first antennae 8- 

 segmented; second antennae 3-segmented; in ascidians. 



9 Enterocolides Chatton and Harant, 1922 



2. Fifth legs biramose, rami of equal length, 1-segmented, exopod 



conical, with a single long apical seta, endopod laminate and 



unarmed; in ascidians cf Paranotodelphys Schellenberg, 1921 



Fifth legs uniramose and 2-segmented 3 



Fifth legs uniramose and 1-segmented, or reduced to mere knobs 8 



Fifth legs replaced by setae, or wholly lacking 11 



3. Caudal rami modified for prehension, armed with claws 4 



Caudal rami not prehensile, armed with plumose setae 5 



Caudal rami not prehensile, naked, without claws or setae 7 



4. Body compressed laterally; brood pouch boldly arched dorsally; 



caudal rami curved downward, each armed with an apical 



claw; in ascidians cf 9 Pachypygus G. O. Sars, 1921 



Body cylindrical; brood pouch exceptionally long and flatly 

 arched; caudal rami laminate, with stout clawlike spines; in 

 ascidians 9 Botachus Thorell, 1859 



5. Distal segment of fifth leg four times as long as wide; caudal 



rami six to eight times as long as wide; metasome segments all 



the same width; in ascidians cf 9 Doropygopsis G. O. Sars, 1921 



Distal segment of fifth leg as wide as long, with 1 apical seta 6 



6. Metasome fusiform; caudal rami three times as long as wide, 



apical setae five times as long as rami; urosome half as long as 



metasome; dredged, 20 fathoms cT Agnathaner Canu, 1892 



Metasome obovate; caudal rami four times as long as wide, or 

 more; setae no longer than rami; urosome one-fourth as long 

 as metasome; in ascidians cf 9 Notodelphys Allman, 1847 (p. 386) 



