^'Twifr''] PliOCKEDlNGS OF TilK NATIONAL MUSKUM. 279 



conN'cx lliiiii t'lic oilier. In tlic widest part it iiieasures 1.) millimeters, 

 wliile tlie leiigtli (Mumls L5A cent imelers. It is \('r>' miieli like (1. curvu- 

 tiis* ol" the Vir<>iiiiii rotomae, llie only diCiereuee heini;' lliat it is not 

 so miicli curved as that. Named i'or Mr. ,1. W. Harvey, tlie collector. 



Cycadeospermum rotuiidatuni I'ont. 

 I'l. XLiii, l'i<;'. ti. 



Several si)eeimeiis of this were se«'ii. The seed was spherical in form 

 and covered with a. smooth parchment lik<' dnial»Ie epidermis, which 

 jooUs like brown enamel, and is often all that is preserved. It is al)ont 

 S millimeters in diameter, it is exactly like tiie seed of the same name 

 found in the Potomac of Vir,i;inia,l bnt is more strictly jilol)ulai' in 

 form, a ditfereiu'C that is juobably i\uv to diflerent etfects (A' pressure. 



A(IE AND AFFINITIES OF TIIE TRINITY FLORA. 



A tyi)ical Mesozoic tlora^ is conii)osed of only four elements. These 

 jire ferns, cycads, conifers, and (Mpiiseta. The tlora of tins ty])e seems 

 to have reached its culmimition in the. -lurassic, but many of its jdants 

 were continued with diminishin<;' numbers thi'oiij;h the Lower Oretace- 

 ons, endin;^' with that ejxxdi. The Wealden of ditferent i)arts of tlie 

 world appears to have Ikmmi the fresli- water and nuirsh equivalent of 

 the lower ]>ortion of the Neocomian, which, in its typical development, 

 represents the marine dei)osits of the Lower ('retaceous. The typical 

 Wealden contains uo element in addition to the four given above, but 

 the lower l\)tomac formation, as seen in Virginia, ai)i)ears to coin(;ide 

 in age with the greater part of the Neocomian, and this gives us, so 

 far as is yet known, the first ai)pearance of angiosperms. The older 'por- 

 tion of the lower Potomac; contains, with a great ]»redoininan(;e of .Juras- 

 sic types, a number of old forms of a-ngiospernis, such as Fi(;oi)hyllum, 

 Protea']»hyllum, Kogeisia, etc. Jn the upper IxmIs of thci same angio- 

 sju'rins become moreal)undant and they are more modern in tyj)e, while 

 the Jurassic element is nuicli diminisluHl. The plants found at (ilen 

 Hose, sliow, so far as can bejinlged from S(» im])eii'ecta. collection, that 

 the Trinity tlora linds its closest resend)lance in the older portion of the 

 low«'r Potomac. There is, however, t his import ant difference: No trace 

 of angiosi)erms, even tin' most archaic, has been found in tlu^ Texas 

 r<'gion. We ha\'e only the foui- elements of the typical .Jurassic tlora. 

 This then makes the Trinity flora somewhat older than that of tin* old- 

 est Potomac. The absence of theaiigios]»erms and the presence of the 

 forms that are found indicate de<',idedly that the Trinity flora is not 

 younger than tlie (earliest stage of the Cietaceous. The numl)er of 



' Monogiiipli XV, 1 1. S. <JcoloKi<'al Siirvc^y, Part i, text, p. 269; Part ii, plates, PL 

 ex XXV, Fig. 17. 



tMouograph xv, U.S. Ocologi.iiil Suivey, Part i, toxt, p. Ii71 ; Part ii, plates, 

 I'l. cxxxvi, Fig. 12. 



