PACHYDERM AT A 407 



In the interval that has elapsed I have been unable to supply 

 further particulars, and unfortunately the original drawings of 

 the worm have been lost. The habits of the parasite remind 

 us of Spiroptera megastoma infesting the walls of the stomach 

 of the horse. Not improbably this singular entozoon may turn 

 out to be identical with Molin' s Spiroptera sexalata, and if so, 

 it may correspond with Spiroptera strongylina. However, 

 Diesing afterwards recognising, as I had done, the desirability 

 of separating this last-named worm from the SpiropteraB proper, 

 formed for it his new genus Physocephalus. He then called the 

 worm Physocephalus sexalatus. If, as is probable, my Simondsia 

 and Diesing's Physocephalus are identical, the species found by 

 Simonds ought to be recognised by the generic title which 

 Diesing proposed. His genus was established about four years 

 before I described my Simondsia. Diesing was evidently lert 

 up to the recognition of the generic distinction of the worm by 

 Molin' s examination and description of the worm. As, in my 

 original account of the worm found by Simonds, I spoke of 

 numerous appendages to the neck, it is evident that further 

 investigation is necessary to clear up the question of identity. 

 According to Molin and Diesing the male Spiroptera sexalata 

 measures rather beyond J" and the female beyond 4" i n length. 

 Neither Diesing nor Molin speak of Natterer's worms as being 

 found encysted. In fact they were free. Molin simply re- 

 marks : " lo ne esaminai in oltre 6 esemplari maschi e 77 

 femine raccolti in parte dal muco che revestiva le pareti dello 

 stomaco, ed in parte dal pasto contenuto nello stesso organo di 

 un Dicotyles albirostris femina ai 24 Aprile, 1826." After all 

 that has been said it may be that my Simondsia paradoxa 

 and Diesing' s Physocephalus sexalata are quite distinct, and that 

 like the large- and small-mouthed maw- worms of the horse 

 (Spiroptera megastoma and S. microstoma) they play a corre- 

 sponding role. Before very long I hope to set this question 

 definitively at rest. 



Passing to the strongyloid nematodes one of the most remark- 

 able and important species is Stephanurus dentatus. In the 

 1 Annalen des Wiener Museums ' for 1839 (s. 232) this worm was 

 first described by Diesing, who employed the generic title as 

 expressive of the crown-like figure of the tail of the male worm. 

 Diesing wrote as follows : " At Barra do Rio Negro, on the 

 24th of March, 1834, Natterer discovered this peculiar genus of 

 worms occurring singly or several together in capsules situated 



