ORTHID A. 227 
are referable to that species. Messrs. Phillips and Salter, in 1848, had arrived at a 
similar conclusion ; but at a later period (1866) the last-named author referred the British 
specimens to Orthis striatula of Conrad, a name that cannot, however, be retained for 
the shell under description, since Schlotheim had already applied it in 1813 to another 
species... Prof. M‘Coy also identifies our British shell with O. ¢estudinaria of Dalman, 
at p. 228 of his large work on ‘ Brit. Pal. Fossils.’ As may be seen from the specimens 
selected for illustration, this species varies a good deal in shape and size, according to age 
and specimen. Fig. 13, however, agrees most nearly with Dalman’s illustration. 
Prof. M‘Coy observes that “the slight convexity of the receiving (ventral) valve, 
the wide and very low cardinal area, and the very much coarser, more separated, angular, 
and less equal ridging of the valves, easily separate the species from the O. elegantula ; 
and the greater size and depression of the valves, as well as the less number of strize at a 
small distance from the beak, separate it from the O. parva. Gothland specimens agree 
in general form, proportional measurements, and in the remarkably low cardinal area ; but 
seem to have the entering (dorsal) valve more obtuse, and the ribbing slightly more regular ; 
but the observed varieties of the Gothland specimens show these to be inconstant, and only 
irregular peculiarities of a few specimens.” I cannot, however, agree with Prof. Phillips 
and Mr. Salter that Atrypa polygramma, Sow., is a large variety of O. ¢estudinaria ; both 
shells being quite distinct. 
Position and Locality. ‘This species is said to have been found in the Llandeilo, 
Caradoc, and Lower Llandovery formations; but it is most prevalent in the first two. 
In the Lower Llandeilo it occurs at Pont-brennaraeth, Llandeilo, and Narbeth, also at 
Pont-dwfn, Haverfordwest; at Shelve, in the upper beds of the Llandeilo; also at 
Great Peraver and Gorrans, Cornwall, in quartzites attributed to the age of the Llandeilo 
Flags. In the Caradoc it is stated to occur at Griig, Llandeilo; Sholes Hook, Haverford- 
west, Cheney Longville, Hollies Farm, Horderley ; Meifod, and Church Stretton in 
Shropshire ; and a number of other localities are recorded by Prof. M‘Coyin his work on 
‘Brit. Pal. Foss.’ From the Lower Llandovery it is stated to have been obtained at Cefn 
Rhyddan, near Llandovery, &c. 
In Scotland it was found at Durness, Sutherlandshire, in Lower Silurian. 
In Ireland it is stated by Prof. M‘Coy to be common in the slates at Ballygarvan 
Bridge, and in other localities in the counties of Wexford, Kildare, Wicklow, &c. 
videlicet ; elevatiores (circiter 30), testae basin fere attingentes; et Aumiliores plus minus abbreviate, 
quarum 2—=3, inter par priorum. 
“Valva minor subplana, 1, in medio longitudinaliter sub-impressa ; suborbicularis, basi truncata, apice 
vero rotundato, minime prominulo. Linea cardinalis quam valve longitudo manifeste brevior. Valva 
major basi gibba, nate prominula, modice curva, valvee minoris convexitatem minime attingente. Sub nate 
areola triangularis impresso-plana, foramine deltoideo brevi. 
“ Obs.—Rostrum quam in O. elegantula minus sed quam in O. dasali magis curvatum ; margo cardinalis 
quam in utraque specie brevior.—Specimina plura consului similia.” 
1 «Min. Taschenbuch,’ pl. i, fig. 6, 1813. This is a shell closely resembling O. resupinata, Martin. 
