.S2 ART. 4. T. IK EDA 



FA'hliivoiilcu. 



I. Proljoscis not bifurcated at apex, l>ut truncated transversely. Sexes 

 of similar appearance. 



A. — Anal hooks arranged in 1 or '2 r-ircles. 2 pairs of segmental 



organs Geiiits Echiuuus. F. 82. 



B. — No anal hook. 1-3 pairs or more of segmental organs 



Genus Thalassemia. P. 82. 



II. Proboscis bifurcated at apex. Sexu.il dimorphism remarkably pro- 

 nounced, 



Xo ana] hook. Unique segmental organs 



Genm Bonellia. P. 83. 



ECHIURUS. 



Anal hooks arranged in a siugle circle. No definite blood vessel. 

 E. wit'cinctus. P. 59. 



THALASSEMA. 



I, Longitudinal muscle continuous. 



A. — Segmental organs in only one pair ; the internal openings 

 of the organ lack spiral lobes. 



a. — Body of a small size. Ventral hooks provided in- 

 ternally with a well developed interbasal muscle 



T. owstoni. P. 62. 



b, — Skin-papillie prominent over the whole surface. No 



interbasal muscle T. fuscum. P. 69. 



B. — Segmental organs in 3 pairs ; ])rovided with spiral lobes. 



a, — The anteriormost pair of segmental organs lie in front 



of the ventral hooks T. inansense. P. 71. 



h, — All segmental organs lie behind the ventral hooks. 

 T. mncosurii. P. GS. 



