NO. 9 cuckler: nematode parasites 139 



Alaeuris galapagensis, new species 

 (Plate 13, figs. 1-7) 



This species was the most abundant in the collection. An identifica- 

 tion and count of the entire collection revealed 668 males and 2,045 

 females of this species. 



These are medium-sized oxyurids with slender, spindle-shaped bodies. 

 The anterior end is truncated, but the posterior end of the female is 

 extended as a long, straight, pointed tail. The male tail is short and 

 rounded. The females (fig. 1) range from 4.52 mm. to 6.49 mm. in 

 length by 0.39 mm. to 0.48 mm. in width. The length of the male (fig. 

 2) ranges from 2.75 mm. to 3.80 mm. and the width from 0.20 mm. 

 to 0.30 mm. 



The body is covered with a clear, thin cuticula, which has indistinct 

 transverse striations about 0.005 mm. apart. There are no cervical or 

 lateral cuticular alae in either sex. The males have well-developed 

 caudal alae. 



The cephalic region is distinct and truncate terminally (fig. 3). 

 The terminal, triangular-shaped mouth (fig. 4) is formed by three 

 simple lips which are distinctly separated from one another by small 

 grooves. The dorsal lip is slightly taller than the ventrolateral lips. 

 There are ten cephalic papillae and two amphids. The papillae are 

 arranged in two circles. In the external circle are four papillae, two of 

 which are situated near the posterior margin of each of the ventrolateral 

 lips. There are no corresponding papillae on the dorsal lip. In the 

 internal circle there are six papillae (fig. 4) ; two papillae are near the 

 anterior margin of each of the lips. The amphids terminate slightly pos- 

 terior to the level of the internal circle of papillae. Two uncertain 

 papilla-like structures could usually be seen in the en face view of the 

 lips but could not be distinguished in the lateral or dorsal views of the 

 cephalic region. 



The lips bound a triangular-shaped mouth. The buccal cavity, about 

 0.025 mm. in depth, has six toothlike projections extending into it from 

 the esophageal wall. Three of the projections are continuous with the 

 external surface of the esophagus, and three smaller, sharp projections 

 arise from the inner surface of the esophagus. A small projection is 

 found on the median anterior margin of the dorsal lip ; no similar struc- 

 tures were observed on the other lips. 



The conspicuous nerve ring encircles the anterior end of the esopha- 



