1883.] 



On the Skeleton of the Marsijjobranch Fishes. 



443 



d. There is a large median cartilaginous olfactory capsule. 

 The Myxinoids go beyond even the adult Lamprey in the following 

 particulars, namely : — 



a. The facial basket-work is much more perfect ; and as this is a 

 generalised condition of the true intra-visceral system of cartilages, it 

 is a very important character ; there is not only a development of the 

 " suspensorium," equal to that of the Lamprey, but the suspensorial 

 part of the hyoid is developed also (it is suppressed in the Lamprey) ; 

 and there is, in Bdellostoma, a large complete first branehial arch, and 

 in both kinds pharyngo -branchial rudiments of the second branchial 

 arch. 



b. The respiratory (branchial) pouches are much more specialised 

 by being carried far back under the spine. 



c. There is not only a distinct sub-cranial intertrabecula, but also 

 a large pre-cranial or nasal median cartilage of the same nature. 



d. The opening of the median olfactory sac is not a mere short 

 membranous passage, but a long tube, encased in a series of cartila- 

 ginous (imperfect) rings. 



e. Correlated with the non-development of the suctorial labial 

 cartilages, there is an enormous development of the lingual, this basal 

 bar becoming not only double, but in front quadruple, and the 

 " supra-lingual " cartilages, which are very small in the Lamprey, 

 and carry only one pair of rows of small second teeth, are in the 

 Myxinoids very large, and carry two pairs of rows of large teeth, 

 with the addition of a median antagonistic " ethmoidal tooth." 



Lastly, the greater development of the intra-visceral (= " intra- 

 branchial ") cartilages is correlated with the suppression of the extra- 

 visceral basket-work seen both in the larval and adult Lamprey, and 

 also in the larvas of the " Anura," generally. 



Morphologists must kindly accept this piecemeal work of mine ; it 

 will take on a form, or frame, some day ; but much of the materials 

 for its completion are still wanting, and, when obtained, the working 

 of them out must not be done hurriedly. 



I may remark, that having just now to work at " the extremity of 

 both ends " of the Vertebrata — the Marsipobranchs and Mammalia 

 — I find the former very excellent as carriers of light to the latter. 

 Everyone will see that by far the greater bulk of the existing Verte- 

 brata are very specialised, each order and class on its own lines, and 

 that any creature to be like a primordial mammal must be very 

 generalised or archaic. 



