BRACHIOPODA. 203 



1S(jO. Rhynchonella,T>k\-wiioti. British Carbon. Bra<:hioiKiiia, pp. 93-10."), pi. xx, fifrs. 1-IH; pi. xxi, 



figs. 1-20 ; pi. xxii, tigs. 1-1 T) ; |)1. xxiii, \\g». 1-22. 

 1860. Rhynchonella, McChesney. Ti-an.s. Chicagd Acad. Sci., vol. i, pp. 49, 60. 

 1802. RhynchontUa, Whitk. Pi-oc. Boston Son. Nat. Hist., vol. ix, p. 2.3. 



1865. Rliynchunella, Davidsd.v. Biitish Devon. Bi-achiopoiia, pp. 62, 6:5, pi. xii, tigs. 12 14 ; pi. xiii, 



tigs. 6-18. 



1866. RhynchoTieUa, Meek. Geological Survey Illinois, vol. ii, p. 1.13, pi. xiv, tigs. 4a, b. 

 1S68. Rhynchonella, Mekk. Geological Survey Illinois, vol. iii, [). 4r)0, pi xiv, tigs. la-d. 



1871. TerehraUda, Quenstedt. Petrefactenk. Deutscljlands; Br-ac.hiopoiien, p. 190, pi. xlii, figs. .")-7. 



1883. Rhynchmtella, Willi.\ms. American Journal of Science, vol. xxv, p. 91. 



1884. Rhynvhimella, Walcott. Monogr. U. S. fieol. Siirv., vol. viii, p. ir)5, pi. xiv, figs. 7, 7a. 



1885. Rhynchonella. Clarke. Bull. U. 8. Geo!. Surv., No. 16, p. — . 



1887. Rhynvhonella, de Koninck. Faune du Calcaire Carbonifere ile la Belgiipie, pt. 6, Brachiopodes, 

 pis. ix, X, xi, xii. 



Diagnosis. Shells with deep fold and sinus ; elevated, and often acuminate 

 on the anterior margin ; more or less sharply plicated, the plications usually 

 being simple, those of the fold and sinus the strongest, and those of the lateral 

 slopes often obscure or obsolete. Pedicle-valve shallow ; brachial valve deep. 

 Teeth supported by vertical lamellae ; hinge-plate similar in structure to that 

 of Hypothyris ; the median septum of the brachial valve is extremely faint 

 when present, but is usually undeveloped. Muscular impressions not large but 

 well-defined and clearly subdivided. Vascular sinuses sometimes retained on 

 the pedicle-valve, always obscure on the brachial valve. 



Type, Conchyliolithus anomites acuminatus, Martin. Carboniferous limestone. 



It is apparent that these shells, in the character of their internal apophyses, 

 are not widely removed from those of the type of Rhynchonella cuboides. The 

 contour of the shells affords a difference of fundamental significance, and its 

 trihedral expression in R. acuminata is the nearest approach, among palaeozoic 

 species, to the form of the typical Rhynchonella, R. loxia. 



The group requires a distinctive name, and the term Pugnax has been selected 

 as it serves to commemorate von Buck's term Pugnacecc, which was tipplied to 

 a division of the Rhynchonellas, embracing the typical forms of this sub-genus. 



This combination of characters appeared in the middle or later Devoniau and 

 during the various faunas of the Carboniferous became prolific in species. 

 Among its representatives in American rocks are R. pugnus, Martin, and R. 

 reniformis, Sowerby, of the Chemung faunas of New York; R. alta, Calvin, from 



