C. L. Boulbnger 
247 
branches of the dorsal ray are usually split at their distal extremities, 
not simple as in the specimens previously described. 
In both sexes the cuticle is often much dilated just behind the 
head, in this respect resembling T. retortaeformis Zeder. I am inclined 
Fig. 3. Trichoslrongylus instahilis Railliet. Spicules. x450. 
Fig. 4. Trichoslrongylus vitrinus Looss. Spicules, x 450. 
to believe that this is not a post-mortem phenomenon, having observed 
it in many living specimens of the latter species. 
The females agree well with those described by Looss (1905). The 
eggs measure 80-95 p, by 40-52 p. 
11. Trichostrongylus extenuatus Railliet. 
{Strongylus gracilis McFadyean.) 
This species is easily recognised by the marked dissimilarity in 
shape and size of the two spicules. I have collected specimens from 
Wye and Tenbury. 
