GENERA OF THE SUBORDER PENTAMEROIDEA 



173 



generically from that of Clorinda. In B. minor 

 Booker the septal plates are more widely divergent 

 than in B. wilkinsont, in which they are subparallel. 

 The latter species is approaching Barrandella, but the 

 former is quite a typical Clorinda. We therefore 

 regard Barranditia as a synonym of Clorinda. 



Genus BARRANDELLA Hall and Clarke 1893 

 PI. 26, figs. 1-3, 5-7; t. fig. 30 



Hall and Clarke. Pal. N. Y., vol. 8, pt. 2, 189.% pp. 241, 

 245, pi. 71, figs. 1-3, t. fig. 173; H.indbook, pt. 2, 

 1895, p. 844, figs. 457-458. 



Genoholotype. — Atrypa linguifera Sowerby 

 1839, in Murchison, Sil. Syst., p. 629, pi. 13, fig. 8. 

 Distinguishing characters. — Barrandella is to 



the genotype. Later Schuchert (1897) regarded it 

 as a synonym of the older Clorinda. Recently the 

 name has been revived by Booker (1926) and Koz- 

 lowski (1929), the latter recognizing Barrandella as 

 a genus and Clorinda as a subgenus, but we prefer to 

 regard both groups as of generic rank. 



Geologic range. — Silurian of North America and 

 Europe. 



American Species 

 Clorinda ventricosa (Hall) 1860 

 ? C.jornicata (Hall) 1852 



European Species 

 Barrandella linguifera (Sowerby) 1839 



^ .. Oh 



<i^"n^-r^"^"^ 



Tf/n 





\J 



Fig. 30. — Serial sections of Barrandella linguifera (Sow.), from the Gotlandian of Dudley, England. After Kozlowski. 

 cr, crural plates (inner plates); ca, carina at limit of crural plates and crural septa; sfr, crural septa (outer plates); 

 sm, spondylium. 



be used for shells having an exterior and a ventral 

 interior like those of Clorinda. Inside the dorsal valve, 

 however, the supporting septa of the crural plates are 

 convergent and unite to form a sessile or nearly sessile 

 cruralium. On the outside of the dorsal valve, when 

 the shell is worn, a single septum is visible, which is 

 the track of the united plates. 



A peculiar internal character of Barrandella, accord- 

 ing to Hall and Clarke, 



is the series of strong vascular [pallial], or ovarian sinuses, 

 which radiate from the umbonal region of the pedicle-valve. 

 These arc complicated with the undefined diductor scars, 

 and are therefore to a certain extent of muscular origin. 

 In Penlamerus fornicalus these are highly developed and 

 produce strong ridges on the casts of the valve; while in 

 P. ventricosus they are more numerous and much finer . . . 

 It was for similarly ridged internal casts that Barrande pro- 

 posed the generic term Clorinda (p. 244). 



Discussion. — Hall and Clarke proposed the name 

 Barrandella with Pentamerus linguifera (Sowerby) as 



Genus GYPIDULA Hall 1867 

 PI. 26, figs. 18, 22-24, 26-29, 31, 32, 34-40 



Hall, N. Y. State Cab., 20th Rept., 1867, p. 163. 

 Hall and Clarke, Pal. N. Y., vol. 8, pt. 2, 1893, pp. 241, 

 247, pi. 72, figs. 15-24, t. fig. 177 [cornis). 



Genolectotype (Hall and Clarke). — Pentam- 

 erus occidentalis Hall 1858, Geol. Surv. Iowa, vol. 1, 

 pt. 2, p. 514, pi. 6, fig. 2 (non P. occidentalis Hall 

 1852); Belanski 1928, Univ. Iowa Studies, vol. 12, 

 no. 7, p. 8. 



Description. Exterior. — Galeatiform, hinge-line 

 short and straight; cardinal extremities rounded; lat- 

 eral profile biconvex, the ventral valve usually having 

 the greater convexity. Anterior commissure rectimar- 

 ginate or sulcate; the ventral fold usually low and 

 defined at the anterior only. Ventral interarea very 

 narrow, defined by low ridges, curved, apsacline to 

 anacline, dclthyrium large, open; beak pointed, in- 

 curved strongly; umbo inflated. Dorsal interarea ob- 



