288 CRETACEOUS PELECYPODA 



OPIS, Defr., 1825, (see p. 276), 



1. Opis repleta, Stoliczka, PL X, Pigs. 9-10. 



O. testa sub-qnadr angularly incequilaterali^ tumida^ umbonibtis attemmtis, valde 

 projicientibus instructa^ concentrice confertim costulate striata; limida lata ovato- 

 cordata, profunda; area minori, moderate excavata ; car dine dent e unico crasso in 

 valvula dextra^ duohus in v. sinistra alterum amplecfentibus instructo ; impressionibits 

 muscularibus i^otimdate ovatis^ hand prof undis ; margine interna obsolete crenata. 



Height of shell (including the prominent beaks) : its length ... 1'13 

 Thickness of same ... ... ... ... : „ ... 0'84 



This is an almost rectangular, strongly tumid species, inequilateral, and with 

 very prominent attenuated beaks, with the surface rather coarsely concentrically 

 striated ; the lunula is larger* and deeper than the area ; the internal margin is 

 obsoletely crenulated. The cast (fig. 9) shows the impression of a large median 

 cardinal tooth in the right and two teeth in the left valve, proving the species to 

 be a true Opis. 



Locality/. — West of Odium, in an earthy limestone ; only the two figured speci» 

 mens were found. 



Formation. — Ootatoor group. 



OPISOMA, Stol., 1870, (see p. 276). 



1. Opisoma Geinitziana, Stoliczka, PL X, Pig. 11. 



Op, testa subtriangulari, angnsta, incequilaterali, umbonibus sub-obtusis antice 

 versus incurvis instrticta, antice rotundata^ postice obtuse angulata et producta^ carina 

 forti et prominenti ab umbonibus ad terminationem infero-posteriorem decurrente 

 suppeditata ; margine inferiori fere recto ; lunula cordiformi^ lata, profunda, intus 

 minute striata, fere dimidio totius altitudinis testce (Equante ; area altudini testae 

 (Bquante, moderate excavata, medio elevata ; supeifcie costulis concentris confertis- 

 simis, in regione areali minus distinctis tecta ; cardine in valva dextra dentibus tribus 

 cardinalibus perlongis instructo. 



Height of shell : its length at the inferior margin 1^26 



Approximate thickness of both valves about equal to the length of shell. 



This elegant form is closely allied to P. bicornis, described by Prof. Geinitz 

 from the Plsener beds of Saxony; it differs from this species by being a little 

 longer and more regularly triangular, while at the same time in the European fossil 

 the beaks are higher and more attenuated. 



Locality, — Near Moraviatoor, in an earthy limestone; only three imperfect 

 specimens were found. 



Formation, — Ootatoor group. 



* In fig. 10a (pi. x) the lunula ought to be somewhat larger ; the figure only shows the internal lunular space, but 

 the shading does not exhibit the thick and broad prominent margins surrounding it. The size of the lunula is well 

 indicated in fig. 9a. 



