126 DE. T. DAVIDSON ON EECEXT BRACHIOPODA, 



very thiu, detached, and elongated, but in Megerlina they are more or less thick, and 

 approach more to those of Megerlla. 



So far back as 1852 (Proc. Zool. Soc.) I stated in my paper, " Descriptions of a few 

 New Species of Recent Brachiopoda," that K. Lamarckiana "is distinct from K. pisum 

 and K. Deshayesii by its somewhat tetragonal shape, stronger and fewer costae, as well 

 as by the details of its loop, relating it more than any of the other species of Kraussia to 

 the section Megerlia," and 1 am glad to find that in 1884 M. Deslongchamps has con- 

 firmed the opinion I expressed in 1852. 



74. Kraussina (Megerlina) Davidsoni, Velain. (Plate XXI. figs. 12-14.) 



Kraussina Davidsoni, Velain, Archiv de Zoologie Experiraentale, 1877, p. 139, pi. v. figs. 23, 24 ; and 

 Malacologie de I'lle de St. Pavil ; Davidson, Report on the Brachiopoda, Voyage of H.M.S. ' Challenger,' 

 Zool. vol. i. p. 21, 1880. 



Megerlina Davidsoni, E. Deslongchamps, Etudes critiques sur des Brachiopodes nouveaux ou peu 

 connus, p. 159, pi. xix. figs. 9, 10, 1884. 



Shell small, rather thick, globose, variable in form, pouch-shaped, longer than wide, 

 or slightly transverse and suborbicular. Dorsal valve convex, with a mesial depression 

 or groove of greater or lesser depth. Ventral valve rather deeper than the dorsal one, 

 longitudinally keeled ; beak short, slightly incurved, and truncated by a large incomplete 

 foramen, margined anteriorly by the umbo of the dorsal valve, and laterally by two 

 small deltidial plates. Surface either partially smooth or radiately ribbed, ribs increasing 

 in number by the interpolation of shorter riblets. Surface crossed by strongly marked con- 

 centric lines of growth. Colour darkish brown, verging on black. Length 4 lines, breadth 

 3 or 3| lines. In the intei'ior of the dorsal valve the hinge-plate is comparatively large and 

 concave, with two eye-shaped peduncular scars between its lateral portions. Septum of 

 very small elevation, extending from the middle of the base of the hinge-plate to about 

 half the length of the valve ; from its anterior extremity arise two deviating Y-shaped 

 lamellee, slightly curved at their extremities ; under these and also attached to the 

 septum are two small rudimentary plates. The bottom of the valves is covered with large 

 projecting tubercles, which are most prominent close to the margin of the shell. 



Mab. This species was collected by M. C. Velain in large numbers at the Island of St. 

 Paul, in 1874, during the Prench expedition to observe the transit of Venus. M. Velain 

 states that these Brachiopoda live in abundance in the interior crater of the island, on its 

 littoral side open to the sea ; that during the ordinary low tides they are scarcely covered 

 by water, and are alternately covered and left bare by the ebb and flow of the tide. They 

 occur in an area of a few yards width, and, consequently, at shallow depths, doubtless 

 because they find those conditions to which they are accustomed in other localities. M. 

 Velain informs me that during his lengthened stay at the Island of St. Paul no other 

 species of Brachiopod was found ; that the shell referred to by Mr. Dall as Kraussina 

 picta, Val., Verb, zool.-bot. Ges. Wien, p. 894, 1865, as from the Island of St. Paul, has 

 been nowhere described, and that the name must be attributed to an incorrect citation. 

 This has subsequently been admitted by Mr. Dall. 



