1910.] Osteology of Solenodoir. Siim/iKiry. 253 



In the proportions of the digits and of the cuneiforms the pes of Solenudoii 

 is suggestive of that of the common rat. 



Phyletic Interpretation of the Osteolocjical Characters of SoJenoclon paradoxus. 



Primitive Marswpio-Placental Characters. General architecture of skull 

 and skeleton. Basifacial and basicranial axis nearly continuous; olfactory 

 chamber relatively large, cerebral chamber relatively small. Interparietal 

 paired; orbitosphenoid invaded anteriorly by ethmoid chamber; pituitary 

 depression slight, without posterior clinoid process; basioccipital very short. 

 Alisphenoids with prominent palatine flanges. Posterior border of palate 

 ridged. General arrangement of ethmoids and maxillo-turbinals. Tym- 

 panic ring-shaped, oblique rather than vertical. Arrangement of following 

 nerve foramina: olfactory, internal auditory Jiieatus, facial canal, fenestra 

 ovalis, foramen lacerum anterius and posterius, sphenopalatine, post-palatine 

 stylomastoid, and condylar foramina (the last occasionally double). Venous 

 foramiina: transverse canal in basisphenoid {cf. Didelphis), ? sinus canal 

 in temporal region, post-parietal, post-squamosal, post-glenoid, post-mastoid 

 foramina. Upper molars derived from the tritubercidar type, lower molars 

 with trigonid and small talonid. 



Tail stout at proximal end, with large chevrons. Scapula with bifid 

 acromion, high spine and large coracoid; a stout clavicle; Humerus with 

 stout crests, entepicondylar foramen and globular capitellum. Manus with 

 five clawed digits, separate centrale, large trapezoid and a "pra^poUex." 

 Ilium rod-shaped. Femur with third trochanter. Pes Avith five well 

 clawed digits, entocuneiform very long, mesocuneiform short, a "prjehallux" ; 

 manus and pes fully plantigrade. 



Points of special resemblance to Marsupials: Vomer with large lateral 

 posterior wings, joining ethmoid scroll. Large venous condylar foramina. 

 A remnant of the tympanic wing of the alisphenoid. Posterior mental 

 foramen beneath m^. 



Primitive Placental Characters. Dental formula derived by slight reduc- 

 tion from 'Ifjjj/, deciduous dentition well developed. Orbitosphenoid 

 pierced by optic foramen and not depressed dorsoventrally in such a way 

 that the opposite sphenorbital fissures are confluent beneath it (contrast 

 Marsupials); alisphenoid relatively small and not entering the glenoid 

 fossa. Optic foramen separate from foramen lacerum anterius. 



Seventh cervical vertebra not pierced by vertebral artery; dorso-lumbars 

 20. 



Many other characters listed under the next heading may perhaps belong 

 also under the present heading. 



