Order III. Slreiiia. 



Fatn. I. Hydrodanialidae. 



Cervical vertebrae six only; rostrum narrow, formed by union of 

 the premaxilla; in front of the anterior narial aperture; tail rounded; 

 rudimentary nails on fore limbs; no trace of hind limbs externally or 

 internally; fore limbs flattened oval paddles; upper lip cleft in the 

 middle into two lobes independently movable, approaching each other 

 or receding simultaneously. 



3. Hydrodainalis. 



Hydrodamalis. Retizius, Kongl. Vetensk. Acad. nya. Handlingar, 

 Stockholm, 1794, p. 292. Type R. gigas, Zimm. 



Jihy/inds. 111. Prodr. Syst. Mamm. et Av., 1811, p. 141. 



No teeth: head very small, comparatively; pectoral limbs small. 

 truncated; tail with two pointed lobes; skin naked; epidermis thick, 

 bark-like; vertebra', 60-63. Species extinct. 



4. gigas. {Afanatiis), Zimm. Geogr. Gesch., 1780, 11, p. 426, fig. 5. 



Typt- Unality. Bering Island. 



Genl. Char. Size very large: fore limb covered with short brush- 

 like hairs. 



Gt\>gr. Dislr. Copper and Bering Islands, Bering Sea. 



Coh<r. Dark brown, sometimes spotted or streaked with white. 



Measurements. Total length, 20-25 f^^' Basal length of skull. 

 660: Hensel, 560. Zygomatic width, 340; height at occiput, 160; 

 least interorbital width, 90; occiput to anterior end of frontal, 300. 

 Skull much broken. Spec. No. 22184 U. S. Nat. Mus. Coll. 



Fam. II. ^Jlanatidae. 



4. Maiiatiis. 



I. '— '; M. ^ to ii=ii = 32 or 52. 

 2—2 &— II- II -' -^ 



Manatus. Storr, Prodr., Meth. Mamm., 1780, p. 41. 



Skull arched, descending rapidly anteriorly from Irontals to 

 nasals; zygomata large and massive; jugal greatly developed. Orbit 

 small, prominent, almost enclosed by bone; anterior nares lozenge- 

 shaped extending behimi orbits. The mandible is massive, with a 



