392 Miscellaneous. premolars, it is closely allied to the Xiphodont Anoplotherium, while in the true molars it is characteristically ruminant, and its position would therefore probably stand thus : Dorcatherium, Poebrotherium, Anoplotherium. Measurements * of the head. . ln -Meatus auditorius externus to infra orbitar foramen 3'1 From point of hook-like process of inferior maxilla to anterior mental foramen 4*35 Greatest width of orbit 1*15 Narrowest part of face, below ossa nasi "2 Width at the corono-condyloid depressions of inferior maxilla 1*6 Width at the coronoid processes 2" Greatest width at the ossa tj'mpani 2*1 Distance between ossa tympani *375 Width of os tympanum "85 Length of row formed by the posterior six superior molars ... 2'5 Notch between the first and second superior premolars '333 Length of row formed by the posterior six inferior molars 2*7 Notch between the first and second inferior premolars '45 Measurements of superior molar teeth. Measurements from bones of fore-leg. Transverse diameter of lower articular surface of os humeri '75 Antero-posterior diameter in depressed portion of same '45 Length of olecranon above the lowest part of the articular surface of the elbow *95 From Silliman's Journal for March 1848. On two new genera of Siliceous-shelled Polygastrica from Patagonian Guano. By Prof. Ehrenberg. From the very large number of the typical generic forms of Poly-gastrica already described and arranged, new genera no longer occur so frequently ; but when they do, the new forms have a greater sci-entific value. During his stay in England last summer Prof. Ehren-• The measurements are taken in English inches and parts of the same.