BY VERA A. IRWIN-SMITH. 811 



from the mouth, at the anterior, to the arms, near tlie posterioi- 

 end, but the structure of its walls is not visible. The pharynx 

 {ph.) is slender, with a slight enlargement at its posterior end. 



The male genital apparatus {t., v.s.) is just visible in outline, 

 and appears to be very similar in structure to that of the other 

 species described. Two, equal, penial sette are present (Text-fig. 

 59, />.*•.). They are 0'066 mm. long, and are very slender, and 

 strongly curved, with enlarged, proximal ends. 



Type-specimen, No. W, 458; in the Australian Museum, 

 Sydney. 

 Xotochd'fosoma crypiocephahim, gen. et sp.nov. Measurements in mnis. 



6 



Total length 1 -QoG 



Length of rost rum 'OSS 



Width behind rostrum ... ... ... ... O'052 



Width of narrowest part behind anterior end (r048 



(Greatest width of trunk ... ... ... ... ()'()66 



Width in region of ventral sette ... ... ... 0*048 



Width at beginning of tail... ... ... ... (rdl,") 



Length from tip of tail to anus ... ... ... 0'140 



Length of tail 0-066 



Length from anus to rows of ventral setie ... 0*048 



Length of body covered by ventral seti>?... ... 0*148 



. Length of bod3^-liairs ... ... ... ... 0*007 



Length of dorsal seta^ ... ... ... ... *01 o 



Length of hairs on rostrum ... ... ... O'Oll 



Length of penial setie ... ... ... ... 0*066 



Length of ventral setse, outer rows ... ... (rO'iO 



Length of ventral set;e, iinier rows ... ... 0*015 



Key to the Genera of the Family CluHosoDiatida',. 



a. Head -swelling well developed, and well marked off from the 

 trunk by neck-constriction; pharynx enlarged in liead- 

 region to form one or more bulbs Cii.^iTOSow a 



aa. No well developed head-swelling, and no definite neck-con- 

 striction; pharjmx not enlarged in head to form bulbs 



NOTOCH.^TOSOM A. 



Key to the Sj^ecies of the Genus Ch(Hfosotna. 

 a. Not more than two rows of ventral sette. 



/) . \Vithout head-setcC C. op/iioccphalum . 



bh. With head-seta^. 



