NO. 10 FfXUIXG OUGANS OF ARACMNIDA — SNOI>r,RASS /I 



Tlic paper by Steeling (1924) on Halarachne otarlae Stcd., a species 

 found in the nasal cavity of the California otter, does not give much 

 concise information on the mouth parts, and the figures are some- 

 what sketchy, but the structure evidently is not essentially different 

 from that of other Gamasides. The chelicerae are said to be enclosed 

 ill sheaths, but the sheath connections are not shown in a sectional 

 view of the head. A subcheliceral epistonial plate is clearly depicted 

 in a cross section, giving attachment to the dorsal muscles of the 

 pharynx. The term "Oberlippe" e\idently refers to the tectum, since 

 Steding says it is a prolongation of the dorsal edge of the body, but 

 tile true labrum is seen in a sectional figure as a lobe projecting over 

 llie mouth from the epislome. 



The description of the mouth parts of Laelaps cchidnimis Berl. 

 given by Stanley (1931) presents some details more clearly than the 

 earlier papers on Gamasides, but in certain respects it is difficult to 

 understand, and the terminology is confusing. The chelicerae are 

 called "mandibles," the dorsal wall of the capitulum (tectum capituli) 

 is said to be prolonged in a long, tlaplike "epistome" ; the large labrum, 

 with its ventral surface continuous into the dorsal wall of the pharynx, 

 is termed the "lingula," and a long dorsal lobe of the labrum is named 

 the vo>ncr. The under surface of the vomer is described as being 

 grooved and fitting over a dorsal ridge of the "lingula." The vomer 

 is a structure not described by other writers. The chelicerae are said to 

 1)C enclosed in sheaths, but the connection of the sheaths with sur- 

 rounding parts are not clearly shown. The long hypostome is split 

 into two tapering lobes (fig. 28 I, list), and from the coxal area at 

 each side of it arise two slender, sharp-pointed processes. The lateral 

 process (a) Stanley calls the "stylus," the mesal process (b) the 

 "maxilla" ; the two processes on each side are loosely locked together 

 by a ridge on the "stylus" received into a groove of the "maxilla." 



Ixodidae and Argasidac— The ticks have a well-developed capitulum 

 witii strongly sclerotic walls (fig. 26 .\-D) ; a wide basal extension 

 (lined in the figures) fits into the so-called "camerostome," and is 

 mostly covered in the retracted position of the head (C). On the 

 exposed dorsal surface proximal to the palps in the female are two 

 arcae porosac (.\, ap), presumably sensory. Between the palps the 

 capitular wall is prolonged into the dorsal walls of tubular sheaths 

 {Chs) enclosing the chelicerae. The ventral wall of the capitulum 

 (B, C) is extended between the i)alps to form the large hypostome 

 (B, Hst), which may be parallel-sided or somewhat siwon-shajx-d, and 

 is generally armed below with strong retrorse teeth. The chcliceral 

 sheaths with the contained chelicerae. and the hypostome constitute 



