392 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 42. 



include three species, of which KocJiia (Loxopteria) Isevis Freeh 

 is first mentioned. To this species our specimens also bear no close 

 resemblance. The second species referred to the subgenus Loxopteria 

 is Sandberger's Avicula dispar. The large valve of that species, as 

 figured by Freeh, bears considerable resemblance to the right valve 

 of our species Cliopteria hicostata (see pi. 50, figs. 1 and 2). 

 Freeh says ^ of his genus : 



Den Hauptunterscliied zwischen Kochia und Loxopteria bildet soniit die Gestalt 

 der kleinen Klappe; dieselbe besteht bei beiden Gruppen aus zwei windschief zu 

 einander gestellten Flachen, welche sicb an einer diagonal verlaufenden Mittellinie 

 beriihren. Bei Loxopteria stossen der Hinterfliigel und der Haupttheil der Schale 

 unter einen einspringender, bei Kochia unter einen ausspringendeu Winkel an 

 einander; bei letzterer Gattung besteht die kleine Klappe aus einem steil abstiirzenden 

 Vordertbeil und einer flugellosen Hinterseite. 



The left valve of Cliopteria, as shown in figures 3 and 7, differs 

 markedly from both Kochia and Loxopteria in the strong over- 

 arching beak and its prominent umbonal ridge (as in the Pterineas 

 with gibbous left valves) cut on the anterior side by a conspicuous 

 longitudinal furrow. 



The close afiinity with Pterinea is shown by comparing the right 

 valves (see figs. 2 and 4) with the corresponding valve of Pterinea 

 as shown in our figure 5a of plate 50. The left valves also bear close 

 resemblances, as seen by comparing figures 3 and 7 with figure 5. The 

 chief difference is in the presence of the two longitudmal ridges on 

 the anterior slope of the species C. hicostata and a single ridge in 

 C. unicosta as shown in the figures 2 and 4 of plate 50. In external 

 appearance the right valve resembles the right valve of the Triassic 

 Cassianella grypliseata Miinster from the St. Cassian beds. 



CLIOPTERIA BICOSTATA, new species. 

 Plate 50, figs. 1, 2, 7. 



Shell subtriangular, cardinal length shorter than height of shell; 

 beak prominent, subcentral overarching; area of right valve high, 

 triangular, striated parallel to hinge margm. Anterior ear of right 

 valve rounded, short but distinct; posterior cardinal extremity 

 rounded but no distinct wing separate from the posterior slope of 

 the surface. 



From the beak of the right valve two strong cordlike ridges pro- 

 ceed toward the front, one near the umbonal ridge and separated 

 from it by a narrow shallow sulcus; the other halfway down the 

 anterior slope and separated from the first by a wide furrow and 

 terminating at the middle of the anterior border (see fig. 2). A left 

 valve of apparently the same species (see fig. 7) shows a deep furrow 

 proceeding from tip of beak on the anterior side of the umbonal 



1 Die Devon Aviculiden Deutschlands, pp. 76-76. 



