NO. 2350. NEMATODE GENUS NEMATODIRUS—MAY, 58 5 



tubes again appear in the lateral fields. The structure of the ap- 

 paratus is particularly interesting as throwing some light on the 

 possible relation between the excretory apparatuses of parasitic and 

 free-living nematodes. 



POSTERIOB END. 



The bursa of the male as found in A\ furcatus and N. filicoUis 

 differs from the others mainly in the relatively gi-eater development 

 of the membrane as compared with that of the rays. The membrane 

 then forms a broader margin around the rays and fills out completely 

 the space between the externo-dorsal and dorsal rays. The minimal 

 development of the membrane is found in N. ahnormalis, where it 

 little more than covers the rays, and the indentation between the 

 externo-dorsal and dorsal rays is so deep that the externo-dorsal ray 

 lies very close to the edge of the membrane. The size and extent 

 of the membrane connecting the two dorsal lobes is variable, and 

 reaches its greatest development in N. neotoma^ where it fills out 

 almost the entire space between the two dorsal rays, giving the 

 appearance of an unpaired dorsal median lobe, except for the pres- 

 ence of a deep median notch (plate 31, figs. 18-20; plate 32, figs. 

 21-23). 



On the inside of each lateral lobe of the bursa are a number of 

 blisterlike, transparent elevations or bosses, already described by 

 Hall as transparent maculae. In N. neotoma Hall describes them as 

 located " around the proximal part of the lateral ray and in the 

 area between the externo-lateral and other lateral rays." In the spe- 

 cies from ruminants there seems to be a fundamental arrangement 

 into two groups, either one of which may be more or less developed 

 or even absent in a given species. One group or field extends along 

 the edge of the membrane, slightly farther in than the ends of the 

 rays, from the central rays to the postero-lateral ray. The other 

 group has the shape of an open V, and is placed so that it forms a 

 triangle with the first group. 



The anal glands of the female were found to show no specific 

 differences. There are in general three groups of anal gland cells 

 and one of caudal cells, but they are variable in size and position. 

 The anal cells are arranged as two latero-ventral groups and one 

 median dorsal group. The caudal cells are located directly behind 

 the dorsal anal cells, and are connected with a ventral thickening of 

 the caudal hypoderm behind the anus (plate 30. figs. 16. 17). 

 DISCUSSION. 



The species here described fall into three distinct groups — the fili- 

 collis group, the mauritanicus group, and the neotoma group. 

 Nematodims neotoina has characters that place it rather close to the 

 genus M ecistocirrus ; long spicules, smaller eggs and the vulva set 

 well back. 



