Palceozoic Bivalved Entomostraca. 399 



towards tlie back edge, but huddles itself low down within 

 the curve of the anterior lobe. The semilunar furrow, 

 forming a narrow ridge or fold in the posterior region of K. 

 Wilckenstana, is absent in K. apiculata. In an old indi- 

 vidual of the latter (fig. 5) there is an uncertain appearance 

 of a slight furrow within the anterior border, but it probably- 

 resulted from an accident. Figs. 1-5 show the gradations of 

 form between the youngest (smallest) and the oldest indivi- 

 duals that have come to hand ; and although no two are 

 exactly alike, they all possess the same essential characters. 

 Figs. 4 a, h, c, represent a valve having the antero-ventral 

 region hypertrophied, as is usual among some species of Bey- 

 ric/iiw and in K. Wilckensiana *. The specimens of K. 

 apiculata^ white and well preserved, are not rare in the upper- 

 most Silurian strata at Slite, Gothland. 



V. Beyeichia, M'Coy, 1846. 



(Anu. & Mag. Nat. Hist. ser. 6, vol. xvii. 1886, p. 345.) 



1. BeyricMa clavata, Kolmodin. 

 (PI. XXI. figs. 6-9.) 



BeyricMa clavata, Kolmodin, Bidrag till Kiinnedomen om Sverges 

 Siluriska Ostracoder, Akad. Afhaudl. &c., 1869, p. 18, pi. 0. fig. 10 ; 

 Jones, Silur. Ostrac. Gothland, 1887, p. 2. 



This Beyricliia seems to be the same as Haidenhain's 

 fig. 12, pi. i. (Zeitschr. deutsch. geol. Gesell. vol. xxi. 1869, 

 p. 171), which he describes as B. Kloedeni] also fig. 11 in 

 Angelin's unpublished "■ tab. A." 



It differs from the ordinary B. Klcede^ii in the relative 

 position and size of its lobes. The gigot-lobe is broad and 

 triangular and often compressed above and almost apiculate; 

 the front lobe is very narrow and curved, and the middle lobe 

 lies down close in the concavity of the latter. The surface 

 has a minute and variable granulation. The marginal area is 

 broad and hollow, and its ventral portion has a series of 

 small, impressed, radiating marks, slighter in some specimens 

 than in others, and the outer rim is strong. 



This is an abundant species, and among about one hundred 

 specimens sent to me from Stockholm the arrangement and 

 relative size of the lobes are remarkably persistent among 

 individuals from 1 to 2^ millim. in length. It is plentiful 

 in the shales of Eksta and Frojel. 



* Ann. & Mag. Nat. Hist. ser. 5, vol. xvii. pp. .340-342. 



