DEVELOPMKxNT OF TllK SKULL IN THE BATJJACIII A. 197 



This bar is very slender all the way to the hasal plate, but it has a small hypo-hyal 

 lobe (Plate 15, fig. 9, city., h.hij.) ; the front open space between the hypo-hyals is less 

 than the basal plate, wliich has no front lateral lobes, has sharp liinder lobes, and 

 normal thyro-liyals {t.hy.). 



The mandible (fig. 9) is long, sinuous, and very similar to that oi Pdodryas, having 

 a lai-ge mento-Meckelian and a low coronoid process {ni.mk., ar.). 



The investing bones are very similar, on the whole, to those of the last kind ; the 

 fronto-parietals (f-J^-) scarcely meet behind ; they have the same divergence forwards, 

 and cover a little more of the fontanelle. 



The nasals (».) are twice as large ; they have a greater surface to cover, and they 

 do this better; yet much cartilage is left naked; their form is normal. The pre- 

 maxillaries (pa^.) are almost transversely placed across the narrowed truncated snout ; 

 both their nasal and palatine processes are normal. The maxillaries are of the 

 average strength and size, the ascending facial plate is enlarged and rough under the 

 point of the nasal. Under the nostril there is a rough suborbicular septo-maxillary 

 (fig. 9, s.mx.) ; it is notched in front. 



The quadrato-jugal (q.j.) is slender, but it is well united with the quadrate. The 

 squamosal (figs. 7, 9, 11, .i(i.) is a large X'^baped bone, with its upper bar diverging 

 forwards, and scooped outside for the annulus ; its descending or main bar is unusually 

 long, and of a good width. The parasphenoid (pa.s.) is only two-fifths the length of 

 the skull, but its main part is broad ; it is but little convex (fig. 9) ; its processes are 

 all pointed, and the basi-temporals are slender. The vomers (v.) are much less than 

 in the last, and yet not small ; their form is very peculiar. They are a wide distance 

 apart, and diverge rapidly forwards ; their main part is a long oblong, and ends behind 

 in a transverse toothed part, which has a triangidai* elevation. There is no post-narial 

 spike, but the pre-narial spike is forked, and the proximal part of this external 

 process is almost notched ofi'from the body of the bone ; the outer fork is the longer 

 of the two. The shorter hind spike would appear to be the homologue of the ordinary 

 post-narial process, and the whole bone is evidently dislocated forwards thi'ough the 

 hypertrophy of the trabecular nasal floor {s. ».!.). 



Long as these vomers are, they are half their own length both from the front of 

 the snout and from the fore edge of the girdle-bone. 



The dentary (fig. 9, d.) is slender, and ends in the middle of the ramus. 



Here we have an assemblage of characters which, in the aggregate, put this tyjje far 

 away from the "norma," and yet most of these differences are in reality gentle modifi- 

 cations of a Ranine skull. 



1. The cranial cavity is both short and shallow. 



2. The auditory capsules are small, liut liave a huge tegminal parotic growth. 



Urodeles (Mennponia, Siren, Cnjptobranchiis, Ac.) the epi-hyal becomes fnsed with the quadrate. In 

 Proteus it is largo, very siaiilar to that of a Siiark, and remains free. 



