Most of these extend through narrow apertures foramina pneumatica - into the hollow bones, sometimes, e.g.
The-considerations are not very striking from a general point of view; but the author adds to the weight of evidence which some of his predecessors had brought to bear on certain matters, particularly in aiding to abolish the artificial groups " Deodactyls," "Syndactyls," and " Zygodactyls," on which so much reliance had been placed by many of his countrymen; and it is with him a great merit that he was the first apparently to recognize publicly that characters drawn from the posterior part of the sternum, and particularly from the " echancrures," commonly called in English " notches " or " emarginations," are of comparatively little importance, since their number is apt to vary in forms that are most closely allied, and even in species that are usually associated in the same genus or unquestionably belong to the same family, 2 while these " notches " sometimes become simple foramina, as in certain pigeons, or on the other hand foramina may exceptionally change to " notches," and not unfrequently disappear wholly.
A single pair, which may pass through foramina ("opesiules") in the cryptocyst to reach their insertion.
They are small rat-like rodents, with one pair of upper premolars, which are mere pins, as is the last molar, and the two pairs of limbs of normal length, with the metatarsals separate; the infra-orbital opening in the skull being triangular and widest below, while the incisive foramina in the palate are elongated.
The incisive foramina are large and usually confluent; the bony palate is very narrow from before backwards; there is no alisphenoid canal; the fibula is welded to the tibia, and articulates with the calcaneum; and the testes are permanently external.