64 ^'. K. GREGORY. 



Parker and Haswell (1897). 



" In some fishes the hyomandibular articulates above with the auditory 

 region of the cranium while the jaws are connected with its ventral end. 

 We may thus distinguish two kinds of suspensorhtm or jaw-suspending appa- 

 ratus, a mamiibnhir sttspensoriitm, furnished by the quadrate, and a 

 hyoidean suspensorium by the hyomandibular ; in the former case the skull 

 is said to be antostylic, i. e., having the jaw connected by means of its own 

 arch, in the latter it is called hyostylic ; in a few cases an ainphistyhc 

 arrangement is produced by the articulation of both mandibular and hyoid 

 arches with the skull" (op. cit., p. 71). 



On page 161 we read that in Hexanchus and Heptanchus : ". . . 

 there is a prominent post-orbital process of the palatoquadrate 

 for articulation with the post-orbital region of the skull (amphi- 

 stylic arrangement)." 



The definitions cited may be criticised on several grounds : 



1. There are several ambiguities latent in these sentences 

 which experience proves to be exceedingly puzzling to the stu- 

 dent : (rt) "jaw " and "jaws " thus used require the most careful 

 analysis to determine which jaws ; upper or lower, are intended ; 

 (fr) a mandibular siispciisorium is no doubt equivalent to " a sus- 

 pensorium furnished by the mandibular or first visceral arch " 

 but if " mandibular " be mistakenly interpreted as referring to the 

 mandible the very pith of the definition is lost ; (c] suspensorium 

 or jaw-suspending apparatus is understood first with reference 

 to the lower jaw, then to the upper; (</) "hyoid" arch is used 

 on this same page (71) as referring to the whole second visceral 

 arch, but on page 161 " hyoid arch " is used of the ceratohyal or 

 hyoid only. 



2. The definition of autostylic does not exclude Notidanus 

 (which Parker and Haswell themselves call " amphistylic ") be- 

 cause in it the hyomandibular takes so small a share in suspension 

 that the suspensorium may be said to be "furnished by the 

 quadrate." 



3. The definition of amphistylic as implying the articulation of 

 "both mandibular and hyoid arches with the skull " is exceed- 

 ingly imperfect. As shown above (Table A, pp. 54, 55) the artic- 

 ulation of both mandibular and hyoidean arches with the skull is 

 not diagnostic of amphistyly since on the one hand both arches 



1 Especially since " mandibular " is used in that sense at the top of the same page. 



