MARYLAND GEOLOGICAL SURVEY 247 



corresponding horizon in the Canadian part of the Kittatinny limestone 

 at Columbia, New Jersey. Specimens fairly well preserved are not 

 uncommon in the Stonehenge limestone, particularly the upper part, at 

 many localities in Maryland. The outcrops around Hagerstown and 

 Funkstown have shown some layers fairly crowded with this brachiopod. 



Occurrence. BF.EKMANTOWN LIMESTONE (Stonehenge member). 

 Numerous localities in Maryland, especially around Hagerstown and 

 Funkstown. Tribes Hill limestone at Fort Hunter, New York, and Kit- 

 tatinny limestone, Columbia, New Jersey. 



Collections. Maryland Geological Survey, U. S. National Museum. 



Family RHIPIDOMELLIDAE 



Genus DINORTHIS Hall and Clarke 



DINORTHIS (PLAESIOMYS) PLATYS (Billings) 



Plate XXXVIII, Figs. 6-8 



Orthis platys Billings, 1859, Canadian Nat. and Geol., vol. iv, p. 438, fig. 15. 

 Dinorthis platys Schuchert, 1897, Bull. U. S. Geol. Surv., 87, p. 216. 

 Plaesiomys platys Raymond, 1911, Ann. Carnegie Mus., vol. vii, No. 2, p. 238, 

 pi. xxxv, figs. 13, 14. 



Description. " Pedicle valve fairly high and convex on the umbo, 

 flat or only slightly convex in front. Brachial valve nearly flat, usually 

 showing a shallow sinus on the umbo. Surface marked by fairly coarse 

 striae, which increase by implantation. There are usually three or four 

 in the space of 2 mm. on the front of the shell. The interior of the 

 pedicle valve shows a small muscle area under the beak, composed of two 

 strong diductor scars, and between them two very narrow adductor scars. 

 Delthyrium narrow. No specimen has been seen which was so preserved 

 as to retain the deltidium. In the brachial valve there is a low median 

 septum. Other details could not be made out." Raymond, 1911. 



Occurrence. STONES RIVER LIMESTONE (Middle division). Maugaus- 

 ville, Maryland. 



The types occurred in the Chazyan at Montreal, Canada. In the Lake 

 Champlain area this fossil occurs in the Crown Point or middle division 



