466 MESOZOIC TIME. 1 



an articulation, for lateral motion, in either ramus of the lower jaw 

 (at a), in place of the usual suture; and, besides, the extremities of 

 the two rami were free, so that they served like a pair of arms in the 

 process of swallowing any large animal whole. 



Of Pterosaurs, remains of several species have been discovered in 

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

 another, eighteen feet. These American Pterosaurs are toothless, and 

 are hence named by Marsh Pteranodonts ; anodont, from the Greek, 

 signifying toothless. 



One of the Kansas Turtles, the Atlantochelys 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 

 was like the young of existing species in its ribs. 



Birds. — While the American Pterosaurs were toothless, many of 

 the Cretaceous Birds had numerous pointed teeth, as first observed by 

 Marsh, who has hence called them Odontornithes. In one group, in- 

 cluding the genus Ichthyornis of Marsh (see Plate V.), the vertebras 

 (Figs. 4, 5) are biconcave, and the teeth are set in sockets (Fig. 3). 

 Fig. 1, of I. victor, is half the natural size ; /. dispar, of Marsh, was as 

 large as a pigeon. In the genus Hesperornis of Marsh (Plate IV.), 

 the vertebrae had flat surfaces, and were like the modern, but the teeth 

 (Fig. 4) were set in a groove (Fig. 2), as in most Reptiles ; the skel- 

 eton is between that of the Ostrich and Loon, and H. regalis, of Kan- 

 sas, was a gigantic Diver, five to six feet in height. There were also 

 toothless birds related to the Cormorants and Waders. 



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

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



Characteristic Species. 



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



nerostomum senarium, Rotalia lenticulina, R. senaria Ehr., Grammostomum phyllodes, 

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

 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. — Astrocmnia Scmcti-Sabce 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) ductus Ag. ; Toxaster 

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



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

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

 ira, etc. 



