BY VEKA IRWIN-SMITH. 313 



face of the lip, with a row of denticles along their margin, is also indefinite. The 

 lower, left, lip does not bear a large median tooth, but appears to consist of a 

 series of three or more fairly sharply pointed lobes, having denticles on their 

 summits. Applied externally to each lip is a thick, hemispherical pad, on which 

 two large papillae are visible. 1'he right lip is 13 ^ from summit to base, the 

 left lip 10 II. The buccal cavity is short and narrow. A capsular armature, if 

 present, is not discernible. Round the base of the lips, the cuticle projects 

 slightly, forming a narrow cephalic collarette ; and, at a distance of 11 to 18 /x 

 behind the collarette, there is a prominent circular ridge, with a deep groove 

 in front of it. 



The oesophagus is long and slender, 1/4.9 to 1/5.3 of the total body length 

 (Text-flg. 10). It is formed of two parts, a short muscular portion followed by 

 a darker glandular oesophagus, the boundary between them being clearly marked. 

 I'he total lengfh of the oesophagus is 1.63 mm., the muscular oesophagus being 

 .26 mm. long and 33 ;i wide. The glandular oesophagus increases gradually in 

 width posteriorly, to a maximum of 96 fi. Its base is rounded and the entrance 

 to the intestine is protected by valves ('I'ext-fig. 11). 



The vulva is situated ventrally at about the middle of the length of the 

 oesophagus, .80 mm. from the anterior extremity of the body (Text-figs. 2, 10). 

 The nerve-ring surrounds the muscular oesophagus a little behind its middle, at 

 a distance of 185 /x from the anterior end, and, on a level with the nerve-ring, a 

 pair of thorn-shaped post-cervical papillae are situated on the lateral lines (Text- 

 fig. 3). The excretory pore opens on the mid-ventral line about '2b fx behind 

 these. 



Ex-tending down the left side of the body, from just behind the left post- 

 cervical papilla, and in the same plane with it, is a continuous, regular, wavy 

 ridge, which bears, on the crest of each wave and therefore to right and left, 

 alternately, of the ridge, an oblique, backwardly-direeted cuticular spine (I'ext- 

 figs. 2-6). No trace of a similar ridge, nor of any other spines exists on the 

 right side, or elsewhere on the body. The spines may be regarded as forming 

 a double row, since they point alternately in opposite directions; but the double 

 row is quite certainly asymmetrical. Except on the spine ridge, the cuticular 

 integument is everywhere transversely striate, the striae being very fine and 

 dense, about 2 ^ apart. 



Anteriorly, the spines begin just on a level with the junction of muscular 

 and glandular oesophagus, about 92 ^ behind the left post-cervical papilla and 

 277 ji. behind the anterior end of the body. Posteriorly, they extend to within 

 1.84 to 2 mm. of the tip of the tail. They are of the same charaetei< throughout 

 the leng-th of the row, having the shape of strongly curved, pointed thorns, slight- 

 ly rugose along the crest, and standing up in low relief from the body. Being 

 colourless and transparent, they can only be made out with difficulty when viewed 

 against the background of the body, especially in the posterior region. Fifty- 

 four spines are found on each side of the ridge, making a total of 108 spines in 

 the double row. They vary a little in size, being smallest towards each end, 

 gradually increasing to a maximum between the vulva and the posterior end of 

 the oesophagus, i.e., from the seventh to the seventeenth pair of spines from the 

 anterior end. Their maximum size is 48 fx. in lengfh, and 25 fx. in height. At 

 the anterior end of the row they measure 22 fj, in length and 7 ju, in height ; at the 

 fortieth pair 33 ,«. in leng-th, and 18 yu in height. The width across the ridge, be- 

 tween the tips of the spines on each side, varies correspondingly from 55 ju at 

 the seventh pair, in the region of the vulva, to 74 fx. at the fifteenth pair, and 51 /* 



