414 Mr. H. A. Baylis on a 



apparently laid when the contents have not advanced beyond 

 the two-cell stage of segmentation. 



Tahiti of Measurements o/F. siamensis. 

 (All measurements in millimetres.) 



c?. ' 2- 



Length 15'9 16-6 



Thickness (maximum) 0"8 0-8 



Length of tail 0-9 1-4 



„ mouth-cavity 1 0"1 



,, anterior portion of oesophagus. Oil 0*13 



„ pi ebulbar swelling 0*27 0*3 



(Esophageal bulb, length 03 0-35 



„ ,, transverse diameter . . - 32 - 37 

 Distance from anterior end to end of 



oesophagus (including bulb) 2'4 2*6 



Distance from anterior end to nerve-ring . 0'6 06 

 ,, „ „ cervical pa- 

 pilla- 1-32 15 



Spicules, length 0S6 



„ breadth 0'09 



Accessory piece, length 021 



Distance from tip of tail to vulva . . 60 



,, „ „ caudal pa- 

 pilla? (?) 1-0 



Size of ova O165x01075 



A generic diagnosis, based on the characters of the two 

 known species, may now be given : — 



FalCAUSTRA, Lane, 1915. 



Ascaroidea [? Oxyuridae] . Meromyarian. Mouth with 

 three equal lips, each bearing two prominent papillae, the 

 pulp of each papilla giving off an inner branch which 

 probably ends in a small sensory papilla on the inner surface 

 of the lip. Mouth-cavity surrounded by a ring of thickened 

 cuticle. (Esophagus divided into a short anterior and a long- 

 posterior portion, both muscular, the latter ending in a well- 

 marked bulb, which is preceded by an oval swelling. Excre- 

 tory pore towards posterior end of oesophagus. Tail in both 

 sexes tapering and pointed. Caudal end of male with ten 

 pairs of papillae and a median preanal papilla (double in 

 F. siamensis). A series of simple, fusiform, muscular, preanal 

 sucker-like organs may be present. Spicules equal, sickle- 

 shaped, each having the appearance of a spicule within a 

 spicule. An accessory piece present. Vulva towards poste- 

 rior third of body. Vagina runs foiward and gives off two 

 opposed uteri, each of which doubles upon itself in a number 

 of longitudinally-disposed U-shaped loops in the anterior or 

 posterior region of the body respectively. Ova large, thick- 

 shelled, with contents only beginning to segment when laid. 



