SKULL AND VISCERAL ARCHES IN LEPIDOSIREN AND PROTOPTERUS. 



63 



Plate III. 



Fig. 13. Protopterus, stage circ. 31. The same reconstruction as shown in fig. 7, seen from the side. 



Fig. 14. Lepidosiren, stage 34. Reconstruction from sagittal sections. The hones are shown in outline. 



Fig. 15. Protopterus, stage circ. 36. Reconstruction from sagittal sections. The bones are shown in 

 outline. 



Fig. 16. Lepidosiren, stage 38. Reconstruction from sagittal sections. The bones are shown in outline. 



ABBREVIATIONS USED IN THE MAIN FIGURES. 



a.g.r., wall of anterior end of Gasserian recess. 



a.n., anterior naris. 



a o.j)., ant-orbital process. 



art., artery given off from aortic root. 



aud. caps., auditory capsule. 



Balk., Balkenplatte. 



has. pi., basilar plate. 



bcr.f., basicranial fontanelle. 



br. 1-5, branchial arches 1-5. 



c.b.c, cartilaginous basis cranii. 



cor. pr., coronoid process. 



c.t., connective tissue strand representing vestige of 



palato-pterygoid cartilage. 

 fi., floor of Gasserian recess. 

 G.r., Gasserian recess. 

 Ii., hyoid. 



h. br., floor of hind-brain. 

 lid., outline of head. 

 hph., hypophysis. 

 hypo., hypoblast. 

 i.e., internal carotid. 

 inf., infundibulum. 

 i.op.c, interopercular cartilage. 

 int.s., internasal septum. 

 j.f., jugular foramen. 

 in., mass of tissue concentrated by advancing tip of 



notochord. 

 Mecli., Meckel's cartilage. 

 mes., mesethmoid. 

 n., nucleus. 

 n.a., neural arch. 

 n.a.v., vestigial neural arch. 

 nch., notochord. 

 occ. arch., occipital arch. 

 occ. pi., occipital plate. 

 o.r., occipital rib. 

 ol., olfactory organ. 

 op.c, opercular cartilage. 

 o.t.p., orbito-temporal process. 

 p., parasphenoid. 

 par., paramandibular cartilages. 

 p.g., pectoral girdle. 



p.g.r., wall of posterior end of Gasserian recess. 



p.o., loop of cartilage round " Pinkus' organ." 



p.n., posterior naris. 



prn., prenasal process. 



pr.b., processus basalis. 



pr.ot., processus oticus. 



p.-pt., palato-pterygoid bone. 



pr.s., prochondral strand connecting auditory capsule 



with occipital arch. 

 p.s., primary sheath of notochord. 

 quad., quadrate. 

 r.n.c, roof of nasal capsule. 

 rud., rudiment of palatine tooth. 

 sh., shelf of cartilage underlying squamosal. 

 sp., spine. 



s.n.c, subnasal cartilage. 

 s.s., secondary sheath of notochord. 

 sup. oc, supra-occipital cartilage. 

 symph., symphysial plate. 

 thai., thalamencephalon. 

 tr., trabecula. 



trab., bony trabeculae of palatine tooth. 

 tr. ant., anterior extension of trabecula. 

 tr.c, trabecular cornu. 

 t.m., temporal muscle. 

 t. marg., taenia marginalis. 

 u.l.c, upper labial cartilage. 



vac, vacuity over highest point of palatine symphysis. 

 y., yolk granule. 



I, olfactory nerve. 



II, optic nerve. 



III, oculo-motor. 



V 1 , ophthalmicus profundus branch of trigeminal. 



V 2 , superior maxillary branch of trigeminal. 



V 3 , inferior maxillary branch of trigeminal. 



VII hyo., hyoideo-mandibular branch of facial. 



VII lat., buccal and superficial ophthalmic branches 



of the facial, and ramus communicans between 



VII and X. 

 VII sup. pal., superior palatine branch of facial. 



IX, glossopharyngeal. 



X, vagus. 



