488 OAKBONIFEROUS l-'OBMATIONS AND KAUNAS OK COLCtKADO. 



IIIIH). Alliiri.-'iiia giibciuiciiliiiii. ISoiHle, Univ. (ieol. Surv. Kansas, Kepi., vol. (i, p. Kiil, pi. 20, li^.s. l-lli. 

 Upper Coal Meaaures; Westport (Missouri), Kansas City, Mont IiUi (Anderson County), 

 Lawreneo, Leeompton. Topeka, Elmont, Grand Summit, Kan.s. 



This form sch'ius to liave appeared in iiteratufc under a nuniinu- of tlitlerent 

 names, several of wliicli have clironolog-ical prioritj- over AUerlsma ni(hcuneatuui. 

 Wclier is doubtless eorreet in referring Pfioladouvya elongata Morton to Allerism.a^ 

 and it seems liivelj' that it is the same form which was subsequently described l)y 

 Meek and Hayden. AlJeris/na ferniiiiale Hall also antedates A. sulxmneat/wm, and 

 was, I am confident, proposed for the same specific type. Meek suggests that 

 A. eimformis Swallow is probably a synonym of A. mtbcuneatwn^ and several others 

 of Swallow's names ma_y also prove to be synonyms. A. capax Newberry is 

 probably distinct. 



The first described of these forms was A. elongahim, and 1 beliexe that this 

 name will ultimatel}' suj^plant the more familiar A. snhcuneatum. I have u.sed 

 Allmnsma terminale for this species, while regarding it as highlj^ probable that the 

 other names were proposed for it, because this is the only instance in which I have 

 been able to convince myself of their identity' by direct comparison of material. 



AUerlsma teriiilnale was described from the same region as A. siihcimeatum and 

 seemingly from the same horizon and the same beds. When the type specimen of 

 A. terminale is compared with the types of A. suhcun'eatmn and other typical mate- 

 rial, it becomes clear that it is only a smaller example of the same species, somewhat 

 •distorted by pressure. The specimen shows compression in an unmistakable manner. 

 The direction in which the force was applied is from above, and the effect upon the 

 valves have been to lessen theii' height, exaggerate their convexit}', and to thrust 

 the umbones forward from their natural position so as almost to overhang the ante- 

 rior edge of the shell. 



AUerlsma terminale is abundant in the Rico formation, especiallj^ at station 

 2342, some of the specimens attaining a large size. Associated with the normal type 

 is a comparatively much shorter form, an example of which is represented b}' fig. 

 6 of PI. IX. It is possible that this should be regarded as a distinct variety. 

 In its proportions it approaches the specimen from New Mexico which White figured 

 as AUerlsma stiheuneatum var. The latter is possibly a little more elongate and is 

 more strongly corrugated by concentric ridges, though this difference is likely due to 

 preservation. From the Hermosa formation a small imjjerfect specimen has come to 

 hand. It is like White's specimen in the particular of its strongly rugose surface, 

 but is perhaps a trifle more elongate, and though considerablj^ smaller than fully 

 grown A. terminale probably had, when complete, about the same proportions. 



Locality and horizon. — San Juan region (stations 2204, 2342); rare in the upper 

 portion of the Hermosa formation, and abundant in the Rico formation. 



