428 



How it came about that so careful an observer as Marshall 

 should represent the pre-spiracular cartilage as embedded in a post- 

 spiracular ligament, is a matter which is readily solved by reference 

 to Parker's classical paper on the skull ot the dogfish '"). Marshall's 

 figure is not an exact copy of Parker's but it cannot be doubted 

 that Parker's figure (pi. XXXVIII fig. 2) was consulted at the time 

 of its preparation. In Parker's figure the pre-spiracular cartilage is 

 seen embedded in a ligament which is called the metapterygoid or 

 pre-spiracular ligament, and the space between the latter and the 

 hyomandibular cartilage is marked cl.l or spiracle. Such a ligament 

 as that represented has, however, no existence in the dogfish. The 

 lower extremity is seen to have the relations of the superior post- 

 spiracular ligament, but the upper end is described (p. 210) as being 

 attached to the "outside of the basis cranii". It is a fictitious ligament 

 made up of the upper end of the inferior and the lower end of the 

 superior post-spiracular ligament. 



The mistake of regarding a post-spiracular ligament as pre- 

 spiracular is rendered the more serious by the importance which 

 Parker attaches to his "metapterygoid ligament". In his description 

 of the skull of the adult dogfish (p. 210) he writes: "The pterygo- 

 mandibular arch is curiously swung from the outside of the basis 

 cranii by two short ropes of fibrous tissue: the hindermost of these 

 is the true apex of the arch, the metapterygoid or 'pedicle', * * * 

 and the metapterygoid band in front of the spiracle is attached above 

 to the skull close in front of the hyomandibular". Describing the 

 dogfish embryo, stage 3, he says (p. 204): "The changes which have 

 taken place in the first postoral (mandibular and pterygoid) are remark- 

 able. The true apex, or metapterygoid is a fibrous band with a grain 

 of cartilage in the anterior lip of the first cleft or spiracle", and 

 again (stage 2, p. 199) : "The apex of the mandible becomes a mere 

 fibrous band in front of the 'spiracle' or first postoral cleft." It is, 

 however, only fair to add that, in spite of this error of observation, 

 the value of the conclusions is not diminished to any great extent. 

 The object of the present note is not to deny that the pre-spira- 

 cular cartilage is the metapterygoid, and consequently the apex of the 

 mandibular arch, but rather to point out that it is not embedded in 

 a ligament, and that there is no such thing as a metapterygoid or 

 pre-spiracular ligament in sharks. 



5) Trans. Zool. Soc, Vol. X. 



