Famiry HAPLODONTID/G. 
= Genus Aplodontia, RicHARDSON and AUTHORS (see beyond). 
< Sciuride or Castorida, of some AUTHORS. 
< Castorine, Baird, Mamm. N. Am. 1857, 350 (united with Castor in a subfamily Castorine of Sciurida). 
= Haploodontide, LittseL0 RG, Syst. Ofv. Gnag. Diiggdj. 1866, 41 (as family of the Hystricomorph series). 
= Haploodontida, Giri, Arrang. Fam. Mamm. 1872, 22 (as family of a special series, Haploodontoidea). 
== Haplodontide, ALston, Proc. Zo6l. Soc. Lond. 1876, 78 (as family of the Sciuromorph series). 
Cuars.— Teeth: 1.33; C. 228; Pm. 3; M. 23 =o *$—7—22:; all root- 
less, prismatic, simple, of unique pattern of the molar crowns. Vertebrea: C.7; 
D.13; L. 6; 8.5; Cd. 11=42. Seventh cervical semicostiferous, without ver- 
tebrarterial canal. Clavicles perfect. Scapula triangular; with prominent spine 
and well-developed acromion and coracoid. Tvbia and fibula not anchylosed, 
though closely apposed below. Ulna with long olecranon; radius perfect, 
admitting of rotatory movements. Carpus and tarsus each with nine bones, 
including an os intermedium. Humerus with well-developed greater and lesser 
tuberosities, deltoid ridge, and tubercle; the inner condyle perforate. Femur 
with prominent greater and lesser trochanters, gluteeal ridge and tubercle. 
A large osseous patella. Pelvis straight and narrow ; tia prismatic, project- 
ing beyond the sacrum. Thorax capacious, contracted anteriorly, with 13 
ribs, 7 sternal, the first borne partly upon the last cervical vertebra. Skudd 
with no trace of postorbital processes (so conspicuous in Sciwride), massive, 
greatly depressed, very broad behind; zygomata widely separated behind, 
chiefly constituted by the malars. Anteorbital foramen low in position, small, 
oval, oblique, transmitting a fascicle of the masseter. Lachrymal large, scale- 
like. Nasals broad, not protrusive. Mandible massive, the descending ramus 
broadly laminar, twisted into the horizontal plane; coronoid high, faleate. A 
large hyoid, connected with the skull by long osseous cornua. Right lung 
quadrilobate ; deft dung bilobate. Salivary glands enormous (as in Castorid@). 
Stomach with the cardiac portion produced into a horn-like process. Liver 
quadripartite, the left lobe with a long process, the Spigelian lobule bifid. 
549 
