466 MESOZOIC TIME. 



an articulation, with regular articulating surfaces for lateral motion, in 

 either ramus of the lower jaw (at a in Fig. 854 D), in place of the 

 usual suture. Besides this, the extremities of the two rami were free. 

 The joint consequently enabled the two jaws to serve like a pair of 

 arms, in working down the immense throat any large animal it might 

 undertake to swallow whole. 



Among Pterosaurs, remains of two species have been discovered in 

 Kansas, that were twenty to twenty-five feet in expanse of wings, and 

 another, eighteen feet. 



One of the Kansas Turtles, the Atlaniochelys gigas; had, according 

 to Cope, a breadth, between the tips of the extended flippers, of more 

 than fifteen feet. The shell of a Turtle is made by the coalescence of 

 the ribs, in connection with the deposit of bone in the skin ; and in 

 the young state the ribs are free. Cope observes, that this ancient 

 turtle, although so large, was like the young of existing species, in its 

 ribs. 



Birds. — A number of Birds have been described by Marsh, from 

 New Jersey and Kansas ; of these, one, the Hesperornis, was a Diver, 

 and five and a half feet high ; four were related to the Cormorants 

 (sea-shore web-footed birds, good fishers, and now common on guano 

 islands) ; five were species related to the Waders (the order contain- 

 ing Snipes and Herons). 



Besides these of modern type, Kansas specimens have been de- 

 scribed by Marsh, which have biconcave verteh'ce, like fishes and some 

 reptiles, and also numerous pointed teeth in both jaivs, a characteristic 

 hitherto unknown among birds. Marsh suspects that it may have 

 had a long tail, like that of the Jurassic Bird of Solenhofen (p. 446). 



Mammals. — Species must have been numerous, as they existed in 

 the preceding age, but no relic of them has yet been found. 



Characteristic Species. 



1. Protozoans Rhizopods.— Textularia Missouriensis, T. ylobulosa, Ehr., Pha- 



■nerostomum senarium, Rotalia lenticulina, R. senaria Ehr., Gi-ammostomum phyllodes, 

 from the Cretaceous of the Upper Missouri, identified by Ehrenberg; Cristellaria rotti- 

 lata D'Orb., Dentalina pulchra Gabb, etc., from New Jersey; Fig. 829, Orbitolina 

 Texana R., from Texas, a species having the form of a disk, slightly conical. 



2. Radiates. — (a.) Polyp-Corals. — Astroccenia Sancti-Sabm R. , Texas ; A. Gua- 

 daloupce R., Texas; Montlivaltia Atlantica Lonsd., New Jersey, etc.; Trochosmilia 

 granulifera Gabb, Chico group, Chico Creek, California; Trochosmilia conoidea Gabb 

 & Horn, New Jersey; T. (?) Texana Con., Texas; Platytrochus speciosus G. & H., 

 Tennessee; Flabellum striatum G. & H., Alabama; Micrabacia Americana M., Ne- 

 braska. 



(b.) Echinoderms. — Holaster simplex Shum. ; H. ( Ananchytes) cinctus Ag. ; Toxaster 

 elegans Gabb. ; also species of Diadema, Hemiaster, Holectypus, Cyiihosoma, etc. 



3. Mollusks. — (a.) Bryozoans. — Numerous species have been described and 

 figured by Gabb & Horn, of the genera Membranipura, Flustrella, Escharipora, Bijlus- 

 tra, etc. 



