IIUAUMOI'OI.A. 



..rla. I 



otherwise I <Jo not see smy difference between the two species. It is to 

 be remembered, however, t.h:it. the Nevada. .s|.e<:inif-n-; do not, .show the cardinal area 

 and that they an; not, quite us w<i\\ preserved as the one you sent to me." 0. ham- 

 buryensin is found in the central part of the Pogonip group of Nevada, a hori/on 

 probably equivalent to the lower portion of the (,'ha/y group of New York. The 

 great difference, geographically and geologically, between the localities of 0. kam- 

 burgenni and the species here provisionally identified with it leads to the belief 

 that the two may be specifically distinct. 



In Minnesota this form is found associated with 0. teatudinaria and is easily 

 confounded with it. Upon examination, however, characters are noticed reminding 

 one of (). tricenaria and other species referred to Orthia in its strict generic sense. 

 The wide cardinal area, narrow delthyrium, simple cardinal process, and the fact 

 that none of the stria; terminate on the cardinal lines, are features of that genus. 

 In 0. hamburyensis the surface striae exhibit a strong tendency towards bifurcation 

 and upon them are series of minute black spots, probably infillingsof the punctse in 

 the shell substance. Since Ortfiix is im punctate and always has simple plicat; 

 this species is better placed in Dulmanella. If this conclusion is correct, there is 



ience to show that JJalmcinella was derived from Orthis. 



/''/< / / locality. Car'-, in the Trenton -.hale* at St. Paul, r. -.on Fall*, Lanefttior' 



Fountain, Minnesota. A No from the top of ti. ft limestone near IIIh Bridge, Kentucky. The 



rimers are from the central part of the I'ogonljj group of the Kureka District, Nevada, where 

 eommoOi 



r:>,ll<:i:l<,r. V{. II. S<:ofl->l, K. O. C)ri':h an'] the wi 



I: 



TK8TUDIWABIA 



PLATE XXXIII. flOH. 17-22. 



' '/UK l-f.t,i<li,,.nri>L IM I.MAN. Kon(fl. .S ! !., fflr 1H27, p. 1 15, pi. If, flg. 4. 



). Or//,t* ttKliiditKiria COM-.A/J. Annual li-port, of t.he New York Geological Survey, p. 3. 



..offy of New York: Keport of the S-joon'] district, p. 394, flg. 3. 

 <i,tl,,.. t, -.1,1.1, ,,? . Jhiflem, p. 404. ) 



OrW.m ' .-A II.u.i.. York, vol. I, p. 117, pi. XXXII, fltf. 1; p. 288, 



pi. i.xxix. UK. t. 



rfa I::;.;. ..I'iiari Naturalist an 'I Oeoloj{lnt, vol. i, p. 40, fl. I. 



'.,IM tf.ntuiHn'i.Ti'1 Boot '.K/ of I' -,ia, vol. II, pt. II, p. 8)>j, fltf. Wji. 



ntliin tmtii'linnri.n BILL '/lot?}' of Oina'la. p. I <',',,:', if. H. 



^'""* ' "4? Wiin -t. of th< :phical Survey* wet of the 100th 



Mcrlrlian, p. 72. 



'In.i.Kii. fJin'-innati Quarterly Journal of .^ierjee, vol. II, p. 20. 

 f trtlu>i t<--'.t,'i<li.n'rt':'i WlinHKI.;. jv. p. Z."<, pi. XII, flj^ 



Or(/a i<-^.i'i,:,L,ii,<i HA;.;. -'":on'J Annual I'^i/irt, New York StaU: Oe</loxlt, pi. xxxiv, 



fit? 1 *. I 4, 

 // tettutlinarla WAIXOTI. Monograph of the ',. S. OeoloK<cal Survey, vol. vlll, p. 72, 



pi xi, flg. 10. 

 1892. Dalmanella tttudlnuria HAI. misAngy of New York, vol. vlil, pt. I, pp. 190, 206, 



pi. v. HK-*- 27, 39. 

 1892. Orthit rogata SAUDE^.V. Bulletin of the Minnesota Academy of Xatural Sclenc/*, vol. Ill, 



p. .rji. pi. v, fix-., i i. 



.onyroy v* Davidson's Monograph of Uritiuh Silurian BrseblopodA, p. 229. 



