78 ART. 4. — I. IKEDA : 



HL At butli t'iid« ul' the body [)roper, a hurny ur ciilcareoiis s^hield. 

 Hüok:s |iieseiit. Longitudinal muscle continuous. Only two retractor 

 inuscles (fused together generally from their origin). 



c:7. — A horny (rarely more or less calcareous) shield at 

 both ends of the body proper. The introvert is 

 excentric, arising i'rom the ventral side of the an- 

 terior or anal sliield. Tentacles few and arranged in 



a single semicircle Geiiu-s Aspidosu'Hon. P. 81. 



It. — A spiral series of calcareous papilh«3 forms the anal 

 shield ; the posterior, or caudal, shield is wanting. 

 The introvert is extruded from the centre of the 

 anal shield Genus Clœosiphon. P. SI. 



PHYMO^OMA. 



I. 4 retractor njuscles. 



A. — Dorsal vessel devoid of contractile villi. No collar-like skin- 

 fold behind tentach^s. 



a, — A single 1)i furcated lixing ujuscle. Tentacles ab(nit 12. 

 The longitudinal muscle divided into 20-21 bundles. 

 Crescent-shaped markings on the dorsal side of 



introvert R svolops. F. 20. 



b. — Fixing muscle single and simple. 



1. — Tentacles about 28. The lougitudiual muscle 

 se[)arated into about 30 bundles. Papillae pro- 

 minent, tegmental organs long and accom- 

 panied by a mesentery along their entire 



length P. Japonu'um. F. 22. 



2. — Tentacles 35-40. Longitudinal muscles, 30-35. 

 Papillœ remarkably prominent. »Segmental or- 

 gans short and accompanied by a mesentery 



along tlie anterior half of their length 



F. pucijivuiR. F. 25. 



B. — Dorsal vessel with contractile villi. A collar-like fold be- 

 hind tentacles. 



Tentacles very numerous (50-80). PapilUe 

 small and low. Ijongitudinal UJUscle varying in 

 the nundier of l)undles P. aidillari'iii. F. 24. 



