FROM THE society's GARDENS. 273 



closely with that of the preceding species. T. phigids IST. also 

 presents a close resemblance in the male genitalia to T. latus. 

 In a revision and splitting up of this large and unwieldy genus, 

 these are facts which should be borne in mind. (Concerning this 

 subject, see also p. 283.) 



Trichodectes cornutus Gervais (12). 



One female and two larvae from Gazella euchore, now known as 

 Antido?'cas euchore Zimm. Gervais's specimens were collected on 

 Antilope dorcas. Taschenberg (13; p. 220) identifies the species 

 with Rudow's T. longiceps (11, p. 110), taken on A. arahica. 

 Neumann (14, p. 626) records it from Hijypotragtos equinus. 

 But, as Piaget remarks, the species requires to be examined 

 again and described with more care. 



Trichodectes hemitragi, sp; n. (Text-figs. 11, 12.) 



The material on which the following description is based 

 consists of 13 females from the Tahr [Hemitragus jemlaicus 

 Ham. Smith). 



This new parasite is of considerable interest, on account of 

 certain features in the anatomy of the mouth-parts, which are 

 figured and detailed below. It is sufficient here to say that the 

 pharyngeal sclerite or lyriform organ, upon superficial inspection 

 apparently absent, proves on dissection to be present, but in so 

 highly modified a form, that it must be considered unique in the 

 Trichodectidae so far examined, while it diverges greatly from 

 the typical form of the organ in the Mallophaga as a whole 

 (compare text-fig. 12 with text-fig. 16). This is the more 

 interesting, as T. hemitragi 5 is unmistakably a Trichodect, and 

 presents, with this exception, no particu.larly novel characters. 

 The male, however, is yet to be discovered, and may prove to 

 rank as a distinct genus. 



In examples of Docophorihs bisignatus, from the Storks and 

 Ibises, I have pointed out an instance (20, p. 134), very similar 

 to the present one, of an abrupt deviation in the form of the 

 oesophageal sclerite from that of the rest of the Mallophaga, 

 whei'e, particularly in Docojjhortos and Trichodectes and in the 

 Ischnocera generally, it presents a fairly uniform appearance. 



It would be premature to discuss the reason for this funda- 

 mental change in the character of this organ, occurring so 

 abruptly among forms not otherwise anomalous, until our know- 

 ledge of the function of the isopogometric apparatus is more 

 exact and fuller. But it is, in any event, a very remarkable fact. 



It may be pointed out that the pharyngeal sclerite is an 

 internal organ, and in both the cases mentioned above is 

 invisible without dissection. In these instances, therefore, a 

 purely sujjerficial. diagnosis could only have resulted in the 

 omission of an important and deep-rooted morphological differ- 

 >ence — a character which, if external, would probably entitle the 



Proc. Zool. Soc— 1916, No. XYIII. 18 



