rill) or till' foi|)iis may remain grossly distinct (.Ijo/iufiiimiix, 

 AriitiilniniNx) ; the l)ull)ar rcRioii is always ratlior cliinKatc, 

 lu'vi'r in tlii' form of a clotinitc Imlli. As a riiU' ono may ilis 

 tinK»>^l> procorpiis and nu'ta('ori)iis in totomount specimens 

 tlir»n);li the idianue in the esoi)liaf;eal lining ( Fijj. 1.">K) as the 

 size of tlie marginal tubes l>eeonies reduced; no forms are 

 known with thickened attachment points for the radial muscles 

 altluingh the muscles themselves are concentered. 



The nuclei of the esophagus of axonolaimoiils are essentially 

 as in Phftiis except that in some forms {Salinlirria viil(iari.s) 

 the six iiosterior radial nuclei tend to assvime a hexa ratlier 

 than a trisynimotry in their arrangement. Tlu' esophago 

 intestinal valve is as elongated as in jilectiuds an<l of slightly 

 different form (Fig. S4 LM^ ; it contains aliout 111 to 1^ nuclei. 



Kepresentatives of the superfamily Monhysteroidea are of 

 three general types, liiiliomoeids, monhysterids and sii)hono- 

 laims all characterized liy a smaller number of radial nuclei 

 than is found in |)lectoids and axonolaimoids. The I.inhomoei 

 dae contains forms with a clavate esophagus which may (Dix- 

 )iu>ltiiniiis) or may not (I.inh<iiiioci(.i) ho terminated liy a well 

 marked nniscular swelling or hulli ; the esophago intestinal 



valve is usually delinitidy I'longaled l.ut rri.iy be rather short 

 ( N/)/i(i(/i(/(iiHiH.v ). In these forms the radial muscles are con- 

 centered and this condition is usually accompanied by thickened 

 cuticular attachment points on the lining (Figs. Kli, H'>, H7). 

 The esophageal hnnen while mo<lified due to these attachment 

 points is devoid of marginal tubes. Forms such as Tripylium 

 carclnicoliim, Trrxchrlliiir/iii pontica and l)i wmohiimus zeclan- 

 (Urns, V. iniiiricditiix have only .'id to T.i radial nucdei, the re- 

 duction or difference in number being in the metacori)U8; the 

 second group of marginals is also apparently lacking in Tcr- 

 .ichiiliiu/i<i. We find in tlii^se forms the same i>eculiar distri- 

 bution of the radial nuclei of the jiosterior part of the bulb 

 previously mentioiu'd in the axonolaimoids (Fig. !HI). The 

 esophago intestinal valve of linliomoidds is often associated 

 with specially differentiated intestinal cells t Triiii/liinii) and 









Vm. 87. A-I> — ThtriitfuH /fpfosun. EI — TfrsfUeUingia pontirn { K — 

 rnrpiis; K — bulbar region; G-I — serial sections throueh csophago-in- 

 testinni valve). J — T>cnmoUtimnn zeelayuii<"HM v. niupricnnus ( I^^hgitudi- 

 nal section through bulb, and esophago-intestinal valve). "' 



Fl(!. 88. EthmoJaimujt revalienms. (A — Stoma tal reRion ; B — ror- 



pus ; r-(; — bulbar roKi<'n ; HI — esophago- intestinal valve) . 



KiG. rt!>, MojmpoMthin hi'.valntn, AC — corpus (A — in stomatal region; 

 H — just posterior to tlie orifice of dorsal gland; C — near base). D-G — 

 bulbar rvgion. H — esophago-intestiual valve. 



All after Chitw. & Chitw.. 1936, J. Wash. Acad. Sc. v. 26 <8). 



85 



