150 rm. e. lonnbed,g o$ the [Feb. 20, 



are not nearly so high as in Bos \ and hardly so high as in Ovis and 

 Gapra. They measure 2-3 mm. in height, but this may partly be 

 due to contraction. The free margins of these walls in the fundus 

 are finely denticulated, but all of them are provided with vertical 

 ridges on their lateral surfaces. The cells are again partly divided 

 by smaller walls into secondary cells, but this is quite irregular. 

 The cellular interspaces are also finely reticulated by small tertiary 

 ridges which carry small conical papillae, and sucli are also found 

 within the tertiary reticulations. This is conspicuous on places 

 where the epithelial covering has fallen off. The reticulum of 

 Ovibos is thus much more differentiated than that of Rangifer and 

 Capreolus, in which the cells are very shallow. The difference 

 between Ovibos and Rangifer, which both lead a similar life, 

 indicates that no parallelism in development has taken place with 

 regard to this organ. This, on the other hand, seems to prove 

 that the suggestion made by Owen 2 , that the shallowness of the 

 cells of the Reindeer's reticulum is due to the fact that the 

 animal obtains so much water by its swallowing snow that any 

 reservoir for water is unnecessary, is incorrect. Ovibos is a repre- 

 sentative of a more specialized ruminant type. 



The diameters of the reticulum of Ovibos are 160 X 210 mm., and 

 those of the psalterium 180 x 230. The latter is thus larger ; and 

 therein Ovibos agrees with Bos, and differs from Ovis, Gapra, 

 and the Cervidce 3 . 



The number of folds in the psalterium is 61, and their arrange- 

 ment is plainly quadruplicate, with folds, or septa, of first, second, 

 third, and fourth order. Eight folds of the first order are con- 

 spicuous, embracing 7 pockets of the first order. There ought, 

 then, to be 57 folds, if it were quite regular, but some few of the 

 fourth order are not developed ; on the other hand, there are some 

 outside the seven pockets belonging to incomplete pockets. The 

 quadruplicate arrangement agrees with that in Ovis, the same in 

 Bos being quinquiplicate. 1 do not think, however, that much 

 stress can be laid upon this character ; this opinion being confirmed 

 by the fact that Garrod has found in the genus Cervus forms with 

 quinqui-, quadri-, and triplicate arrangement of these septa '. 

 Capreolus is said to have a quadriplicate arrangement of septa in the 

 psalterium ; but before me lies a specimen which has only a 

 triplicate arrangement, without the slightest trace of the fourth 

 system of folds. Likewise I have a psalterium of Gapra with only 

 a few indications of the folds of the fourth system \ 



The psalterium-folds are beset with conical papillae, usually 

 almost as broad as high (about 1| mm.), but more acute towards 

 the free margin of the folds than at their bases. At the opening 



1 Vergl. Auat. d. Hausthiere, achte Auflage, 18%. 



2 Anat. of Vertebrates, toI. iii. p. 472. 



3 At least Capreolus, Cervus dama, and C. elaphus. 



4 Proc. Zool. Soc. 1877, pp. 2 et seqq. 



' Boas has also pointed out the variability of this organ (Morph. Jahrb. 

 1890). 



