PLATE Va. 



(Fijfures 2, 4, IS-Jl, 24-40 liv K. ICmmoxs; 1, :!, 5-14 by K. 1'. WimiiKi.ii ; 1.") I,\ K. U. Mkkk ; iJ Ijv riiiLii- A.si ; 



■23 by i. C. McCoxstLL. ) 



Legend. A- Deltidium. a'. Posterior adductor impressions, 



j. Cardinal process. r. Diductor muscular impressions, 



fj). Crural plate. p. Pedicle-muscular imjiression. 



t. Teeth. o. Ovarian impressions. 



1). Sockets. V. Vascular markiuirs. 

 a. Anterior adductor impressions. 



HEBERTELLA, nom. nov. 



Page 198. 



•Okthis sinuata, Hall. 



Fig. 1. The interior of a pedicle-vah-e ; giving the chai'acter of the muscular area, ovarian and vascular 



. markings. 

 Fig. 2. An enlargement of the muscular area of the pedicle-valve ; showing the large diihictor (;•), lineal 



central adductor (a) and the pedicle-scar (p). X 2. 

 Fig. 3. 'I'he inteiioi' of a bi'achial valve. 



Fig. 4. The muscular and deltidial area of the brachial valve; showing the iiari'inv, slightly tliickened 

 cardinal process {j), the large ci'ural plates and the (piadripartite imi>i'ession of the adductor 

 muscles. X 2. 

 Fig. 5. The exterior of a brachial valve. 

 Figs. 6, 7. Cardinal and pi-oiile views of the same specimen. 



Fig. 8. Exterior of the pedicle-valve ; the ai'ea and delthyrium of the opposite valve showing. 

 Hudson River gi-oup. Chicmnati, Ohio. 

 For further illustration see Pala-ontology of Ohio, Volume I, plate ix, tig. 4. 



Orthis sixuata, Hall. (?) (Compare 0. Maria, Billings.) 



Fig. 9. A view of the brachial valve and profile of a specimen doubtfully referred to this species. 



Hudson River group. , Ofiiu. 



Fig. 10 = 19, by error. 



Orthis occidextalis, Hall. (?) 



Figs, 11, 12. Views of a small specimen with coarse, simple plications, and the median sinus iucipieutly 

 develojied ; probably the yoimg of this species. 



Hudson River group. iSamimah, Illinois. 



Orthis insculpta, Hall. 



Fig. 13. The interior of a pedicle-valve ; showing the muscular, vascular and ovarian markir.gs. X -• 

 Hudson River group. Oxford, Ohio. 

 For further illustration see Palseontology of Ohio, Volume I, plate ix, tig. 1. 



PL.ESIOMYS, NOM. NOV. 



Page 1(16. 



Orthis retrorsa, Stiltei- (= 0. C'arlei/i, Hall). 



Fig. 14. The interior of a pecicle-valve ; showing the short dental lamellie, subqnadrate muscular area, 



the vascular and ovarian makings. 

 Fig. 15. A view of the pedicle-valve of the orignal specimen ; showing the high area and retrorse beak of 



this valve. 

 Fig. 16. Profile of a large individual ; showing the gi-eat convexity of the brachial valve and the degree of 

 resupination of the beak of the pedicle-valve. 

 Hudson River group. Oxford, Ohio. 

 For fui'ther iUustratioti, see Palteontology of Ohio, Volume I, plate xi, tig. 7. 



Orthis sobquadrata, Hall. 



Fig. 17. The intei-ior of the pedicle-valve ; showing the component scai-s of the subcpiadrate muscular are;i, 



the lateral ovarian areas and the vascular impressions over the pallial region. 

 Figs. 18, 19. Brachial and caidinal views of a normal individual. 

 Hudson River group. Oxford, Ohio. 

 For further illustration, see Palseontology of Ohio, Vohuue I. plate ix, tig. 2. 



