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Strongylids of Horse 
information on the structure and development of some of the lesser known 
species as well as remarks on their geographical distribution. 
The majority of the species of horse sclerostomes seem to have a very 
wide distribution, many forms being now known from five continents, there 
seem however to be a few (e.g. certain species of Triodonto'phorus) with a more 
restricted range, these are discussed below under the appropriate headings. 
Genus Strongylus Mueller, 1780. 
(.Sclerostoma Rudolphi.) 
1. Strongylus equinus Mueller, 1780. 
This species was found in almost every horse examined in the Punjab; 
from the account given by Looss (1902) and my own observations it appears 
relatively more abundant in the East than in Europe. I have found S. equinus 
of rather uncommon occurrence in England, and Kotlan (1919) has also called 
attention to the comparative rarity of the species in Hungary. 
2. Strongylus edentatus (Looss, 1900). 
The second of the larger species of Strongylus was found in abundance at 
Lahore, both in fresh material and among the specimens preserved in the 
Veterinary College collections. 
3. Strongylus vulgaris (Looss, 1900). 
This, the smallest of the species of Strongylus , was also found to be of 
common occurrence. 
Genus Oesophagodontus Railliet and Henry, 1902. 
4. Oesophagodontus robustus (Giles, 1892). 
Only a single specimen of O. robustus occurred among some material 
labelled Sclerostoma sp. in the Punjab Veterinary College collection. The worm 
was in a much damaged condition, but there is little doubt as to its correct 
identification. 
This species was originally described by Giles from horses and mules in 
India, I was able to record its occurrence in horses in England (1916) and it 
has recently been rediscovered in that host in Canada (Ransom and Hadwen, 
1918) as well as in a Chapman’s zebra from the London Zoological Gardens 
(Turner, 1920). 
Genus Triodontophorus Looss, 1902. 
Five species of this genus have now been recorded (cf. Boulenger, 1916), 
their geographical distribution presenting certain features of interest. 
The type species, T. serratus, as well as T. minor, were originally described 
by Looss from Egypt (1902) and until recently were not definitely known to 
exist elsewhere. I was able to show (1916) that the British representatives of 
