768 



GEOLOGY 



large prey. As these strange birds attained a length of six feet in 

 some cases, they were doubtless formidable enemies to the sea life; 

 on which they choose to feed, and their victims may have embraced 

 fish and reptiles of considerable size. As they have been found in 

 Kansas, Montana, North Dakota, New Jersey, and Kngland, they 

 probably frequented the epicontinental seas somewhat widely. 



and belong more to the sea life than to 

 the land life from which they sprang. 



The second type, Ichthijornis (Fig. 

 521), was scarcely larger than a pigeon, 

 endowed with great power of fligln 

 indicated by the strong development of 

 the wings and keel. At the same time, 

 their legs and feet were small and 

 slender. They had teeth set in socket s. 

 Their biconcave vertebrae and other 

 skeletal features, as well as their small 

 brains, suggest reptilian relationships, 

 Their habitat was the same as that of 

 Hesperornis, and yet the two \ 

 farther apart, structurally, than any 

 two types of birds now living (Marsh ). 

 An important change took place in the fish of the sea. in the 

 transfer of dominance from the older types to the teleosts. This 

 change set in during the Comanchean, and was complete by the 

 middle of the Cretaceous. Though modern in type, the species 

 were in the main ancestral, and some of them are not yet extinct. 

 The sharks and rays were chiefly of the modern types, though not 

 of living species. 



Invertebrates. The most notable departure from the p 

 dents of the preceding ages is the prominent place which the 

 rhizopods or foraminifcrs take in the record. They made lar.ii' 



Fig. 521. Ichthyornis victor, 

 a Cretaceous toothed bird 

 of flight, Vio natural size. 

 (Restored by Marsh.) 



Fig. .522. CKKTA< !:<> i s l-'ussn.s. a-e, Echinmli-nns: it, /'i-ilinnps-'- 

 Chirk; 6, Cassidulus subfjumlratus Con.; <; liotrenpuynx nlubamenxiHl 



f/ and e, S>i(cn/'<i InniSilnln (Mark. /, </, :md //, /V/rr///Wx: /. fWrv 

 180118 M-ck; i/, Idnni'iircd w/j/v/.srr/Jx/s < )\v-li. :illi'l to the arras of tn 

 h, Inwramwt rnnu.ri-nii M. :m<l II. /'-/. (i<istrn/>'!.^: /'. \rptuni'll<i 



tertus M. :'n! II); j. A-pfiorrhais prokibiatn (Wliitn: /.-. />/*//. 

 nebrascensis (]'.. :unl B.)j / /'//''"/"* bairdi (M. and H.) 



