1891.] ORGAN IN THE CROCODILIA. 151 



mississippiensis (figs. 1 and 2), the bullate cavity of the vomer of the 

 former (vo.'") might appear to He vcithin the area of, and indeed to be 

 represented by, the anterior divisions of the maxillary sinus of the 

 latter (sn.). The distinctness in the Caiman of the tvpo bones 

 named shows, firstly that this cannot be the case, and secondly 

 tliat the extension of the maxilla of Alligator misslssipiensis into the 

 region of the palatine lobe of the vomer of Caiman niger must have 

 been one of the changes resulting from the loss of the latter, should 

 that have been brought about as supposed. 



The premaxillo-maxillary sutures of the adult Alligator mississip- 

 piensis meet at all points, and the two pairs of bones form a con- 

 joint and complete osseous roof to the mouth. It has, however, 

 hitherto escaped notice that matters may be otherwise in the young of 

 this species, for the sutures in question may be, in them, interrupted 

 by a couple of rounded fenestrse (fig. 6, f. pi.') having the cus- 

 tomary relationships of the prepalatine foramina of other Amniota. 

 On cutting away, from above, the greater portion of the olfactory 

 organ, and then carefully dissecting off the mucous membrane and 

 cartilaginous floor' of the same in the largest juvenile oi Alligator 

 mississippiensis which I have examined (total length 1 12 centim.), 

 I was surprised to find a couple of small sacs (_/<?. ?, fig. 4) lying 

 within the embrace of the prepalatine foramina. Each is a firm and 

 resistant structure, invested in a fibro-cartilaginous wall, and con- 

 taining a soft (? vascular) lining. I have been unable to trace any 

 connection either between the capsules of these sacs and the car- 

 tilaginous alse of the olfactory vi^all, or between their central cavities 

 and those of either the mouth or the nose. So far as I have been 

 able to examine them, they appear to be to all intents and purposes 

 closed vesicles, vestigial in nature. That they correspond in position 

 with at least the antei'ior extremities of, and must be looked upon 

 as directly related to, the bullate palatine lobes of the vomers of 

 Caiman niger, I hold it to be sufficiently clear ; and it remains now 

 to seek the clue to the remaining portions of the latter bones. 



On laying bare the nasal organ of any Crocodile from the side, it 

 will generally be found, on removing the mucous membrane, that 

 the anterior truncated extremity of the vomer is buried in a more or 

 less powerful ligament {Ig., fig. 4) which runs forwards towards the 

 premaxillary region. Among those genera and species which I have 

 examined, this ligament is most powerful in Osteolcemus tetraspis 

 of W. Africa; in my specimen of that animal it assumes the form 

 of an upturned fold or keel, which, as viewed from the side, continues 

 forwards as it were the body of the vomer, instead of the more 

 general one of a cord-like structure continuous with its tapering 

 extremity. This vomerine ligament (Ig., fig. 4), as already stated, 

 may be traced forwards into the premaxillary region ; its fibres 

 usually there blend with those of the premaxillo-maxillary peri- 

 osteum, and when (as for ex. in Crocodilus palustris, fig. 1) a 

 " palatine process " of the premaxilla {p.p.) is present, they may 

 be traced to an insertion into that. In the young Alligator missis- 

 ^ A portion of this is represented in situ at ns.f. in fig. 4. 



