Mesozoic and Ccenozoic Geology and Paloiontology. 57 



Dr. Jiimes Schiel* found the Cretaceous rocks west of Fort Atkin- 

 son, and described Inoceramus pseudo-mytiloides. W. P. Blake, 

 from the fossils collected by Capt. John Pope, identified these rocks 

 on tl e banks of the Red river, near Preston; Big Springs of the Col- 

 orado; Elm Fork of the Trinit}' river; and a point 20 miles east of the 

 Sand Hills, on the Llano Estacado. 



In 1856, William P. Blakef announced generally' the Cretaceous 

 age of the extensive table lands on the 35th Parallel from the 101st 

 to the 110th Meridian, known as the Llano Estacado. Though Wis- 

 lizenus as early as 1848 had described it in the blufl's of Gallinas 

 Creek, and Dr. Schiel, Dr. Eandall and Lieutenant Simpson as well 

 as Jules Marcou had testified to its existence in various places in the 

 exposed bluffs found upon these plains. The strata are nearly hori- 

 zontal, and principall}' white or grey and highly calcareous, but some- 

 times intercalated with gre}' or blue marl or clay. Prof. James Hall 

 described, from False Washita and other localities in the west, 

 Gryphcca ijitcheri, var. navia. 



INIeek & Hayden;J; described, from near Fort Union, Nebraska (later 

 called Fort Union Group), Cyclas formosa, now SphoRriumformosum, 

 0. subellipticus, now 8. subelUpticum, Bulimus teres, now Columna 

 teres, B. vei'iniculus, now C. vermicula, Pupa helicoides, Limnea ten- 

 uicosta, which is made the type of the genus Pleurolimnea, Physa 

 longiuscula, now Bulimus longiusculus, P. rhomhoidea, now B. rhom- 

 boideus, P. nebrascensis, Velletia minuta, now Acroloxus minutus, 

 Paludina leal, now Vlviparus leai, P. retusa, now V. retusus, P. 

 leidyi, now V. Icidyi, P. trochiformis, now V. trochiformis, Valvata 

 parvula, Melania minutula, now Ilicropyrgus minutuliis, 3£. multis- 

 triata, now Campeloma mult 1st riatum, M. nebrascensis, now Goniobasis 

 nebrascensis; from Moreau river, Cyrena moreauensis, now Corbicula 

 moreauensis, Gyrena intermedia, now Corbicula nebrascensis; from the 

 Bad Lands of the Judith river, Gyrena occidentalis, now Corbicula 

 occidentalis, Corbula subtrigonalis, C. perundata, C. mactriformis 

 TJnio priscus, Physa subelongata, now Bulimus subelongatus, Planor- 

 bis subumbilicatus, Paludina vetula, now Campeloma vetulum, P. con- 

 radi, now Viviparus conradi, Melania convexa, pow Goniobasis con- 

 vexa; from Fort Clark, Bulimus limnwformis, now Thaumastus limncB- 

 formis, Paludina multilineata, now Campeloma multilineatum, P. 

 peculiaris, now Viviparus peculiaris; from Little Horn river, Planor- 



* Expl. <fe Sur. R. R. Miss. River to Pacific Ocean, vol. 2. 



t Pacific R. R. Sur. vol., 3. 



t Proc. Acad. Nat. Sci., vol. 8. 



