On the Anatomy and Pliylogenetic Wsition of Polypteriis. 39^ 



Protractor hyomaudibularis and splnicular are only portions, may be 

 well compared to the same muscle in Heptanchus. So also the Re- 

 tractor hyomandibularis and opercularis and the Intermaxillaris posterior 

 which are actually continued into the fold of the integument repre- 

 senting the opercular mantle. 



The Adductor mandibulae with its division into masseter, tem- 

 poral and pterygoid seems at first sight very different from the Se- 

 lachian adductor. However in Folypterus the temporal and pterygoid 

 are supplied by one nerve branch and have a common tendon of at- 

 tachment. They lie internally to the maxillary and mandibular nerve 

 and may be considered to have arisen by the partial division of a 

 single portion of the primitive Adductor mandibulae. In several Se- 

 lachii e. g. AcantUas (Vetter) there is an anterior portion of the Ad- 

 ductor taking its origin from the skull, and separated from the rest of 

 the Adductor by the maxillary and mandibular nerve (Vetter , in : 

 Jen, Z. Vol. 8, tab. 14, fig. 3). Oiie may therefore conclude that this 

 latter muscle represents the pterygoid and temporal of Folypterus. 



Interarcuales superiores, Adductores arcuum visceralium (with the 

 possible exception of that on the hyoid arch) and a Trapezius corre- 

 sponding to those of Selachians are not present in Folypterus. 



The Levatores arcuum and Interarcuales ventrales are as Vetter 

 has shown derived from the Interbranchiales of Selachians. 



It is on comparing the muscles of Folypterus with those of Uro- 

 deles that the most striking resemblances are seen. With the loss of 

 the hyomandibular in the latter and the fusion of the quadrate to the 

 skull the Levator maxillae superioris naturally disappears while the 

 Retractor hyomandibularis shifts its attachment somewhat and 

 becomes the digastric. The Intermaxillaris anterior and posterior 

 are almost identically alike in Folypterus and some Urodeles. With 

 regard to the jaw muscles one has but to take into account the reduction 

 and imbedding of the dermal bones inUrodela to perceive that in all mor- 

 phological essentials Folypterus agrees closely with such a form as Am- 

 phiuma, the only difference being in the method of origin. Especially 

 close is the resemblance in the details of the nerve supply and the 

 topographical relations of the Ramus maxillaris superior to the masseter, 

 temporal and pterygoid. 



The Levatores arcuum correspond. In the Interarcuales ventrales 

 of Folypterus is seen the commencement of the shifting of ventral 

 attachments from the basibranchial, or more primitively from a median 

 raphe, to the preceding arches which becomes so marked in Urodeles. 



