442 THE PALEONTOLOGY OF MINNESOTA. 
[Ortbis (Dalmanella) testudinar!:!. 
Original description: "0. testa confertissime striata, costis subalternis eleva- 
tioribus; valva minori subplana semiorbiculari; majori basi gibba, nate prominula 
nutante. Locus. Ostrogothia ad Borenshult, in calce cinera. Longit. 15 mm., 
latit. testae 15, lat. valvye minoris ad basin 12 mm., crass. 7 mm. 
"Species quasi media inter 0. elegantulam et 0. hasalem, ad utraque distincta 
ambitu magis orbiculari, minime ad cordatum tendente, prsesertim vero costarum 
radiantium ratione, quae enim duplicis sunt generis, videlicet; elevatiores (circiter 30), 
testae basin fere attingentes; et humiliores plus minus abbreviatae, quarum 2-3, inter 
par priorum. 
" Valva minor subplana, 1, in medio longitudina liter subimpressa; suborbicu- 
laris, basi truncata, apice vero rotundato, minime prominulo. Linea cardinalis quam 
valvae longitude manifeste brevior. Valva major basi gibba, nate prominula, modice 
curva valvge minoris convexitatem minime attingente. Subnate areola triangularis 
impresso-plana, foramine deltoideo brevi. 
"Obs. Rostrum quam in 0. elegantula minus sed quam in 0. basalts magis curv- 
tum; margo cardinalis quam in utraque specie brevior. Specimina plura consulti 
similia." 
The following description of 0. emacerata Meek (not Hall)=0. testudinaria, var. 
meeki Miller, is given, as it applies to this species in all of its details, except that the 
former is larger and more robust than in the majority of specimens usually referred 
to 0. testudinaria: "Species small, plano-convex, rather depressed, transversely 
truncato-suboval, the length being about five-sixths its breadth [sometimes as wide 
as long]; hinge-line perhaps always a little shorter than the greatest breadth of the 
valves; lateral margins generally rounding to the hinge, most prominent at, or a 
little behind the middle, and rounding to the front, which is usually somewhat 
straightened, or very faintly sinuous, at the middle; or presents a regular semi- 
circular outline. 
"Dorsal valve nearly flat, or slightly convex on each side of a shallow mesial 
sinus, that commences very narrow at the beak and usually widens rather rapidly 
to the front; beak very small, scarcely projecting beyond the edge of the area, and 
not incurved; area low at the middle and narrowing off to nothing at the lateral 
extremities of the hinge, slightly arched, and directed obliquely backward; foramen 
[delthyrium] very small and filled by the [large trilobed, striated] cardinal process. 
Interior very shallow anfl provided with a slender mesial ridge that extends about 
halfway forward from the hinge, between the muscular impressions, which are not 
usually well defined; scars of posterior pair of adductor muscles smaller and usually 
deeper than the anterior and situated close back under the brachial processes; those 
of the anterior pair three or four times the size of the posterior [commonly not more 
