118 DE. T. DAVIDSON ON EECENT BEACHIOPODA. 



transmitted liglit, the inwardly inclined tubes are very distinctly visible, especially on that 

 portion of the shell nearest the beak. The tubes are more depressed in £. rosea than in 31. 

 Cimingi. Another distinction which I notice between the two shells is that B. rosea, when 

 examined under a hig-her power of the microscope by transmitted light, shows a more dis- 

 tinctly marked imbricated structure than is seen in M. Cumingi. In the latter species the 

 prismatic structure is seen to be bent around the tubes in a manner not observable in the 

 former. I have noticed this bending of the prismatic structure around the tubes both in 

 Froductm and Chonetes. The real appearance of the perforations as they are seen on the 

 surface of the shell appears to be due to the angle at which the round tubes reach the 

 surface, — the more slanting the tubes within the shell the more oval will be the openings 

 of the perforations. Another point I notice in connection with these perforations 

 is, that from the middle of the valve, on each side, the tubes or canals incline outward 

 and upward towards the beak, and where there is a tendency to any folding of the 

 shell the tubes diverge on each side of the fold." 



Subfamily Kraussinin^. 



Genus KRAUSSINA, Davidson, 1859. 

 In 1852, while examining the interior of the valves of Terebratula rubra, Pallas, I was 

 struck with the marked differences and peculiarities they presented, and in vol. ix. 2nd 

 ser. of the 'Annals and Magazine of Natural History' I proposed a genus Kraussia, 

 subsequently (1861) altered to Kramsina, for the reception of T. rubra and four recent 

 species. The shells are subcircular, with a nearly straight hinge-liue ; beak truncated ; 

 foramen large and round ; deltidial plates small, not united ; beak-ridges well defined, 

 leaving a flattened space or false area between them and the hinge-line. In the interior 

 of the dorsal valve there are two wide, eye-shaped muscular impressions close to the hinge- 

 line, with a small cardinal process between them. A mesial septum of small elevation 

 extends to half the length of the valve, from the anterior extremity of which rise t\^"o 

 oblique or deviating lamellse, laterally expanded ; no other apophysary system for the 

 support of the labial appendages is present. The ciliated arms are unusually small, their 

 fringes not extending to more than halfway towards the border of the shell ; in the first 

 part of their course, from the mouth forwards, the cirri are few or wanting, the whole 

 brachial apparatus being supported by the small forked process above described, no other 

 part of the apophysary system being calcified. This genus has been generally adopted. 

 I have included in it Kruussma rubra, Pallas, K. cognata, Sowerby, K. Deshayesi, 

 Davidson, K. pismn, Lamarck, K. Lamarckiana ^ Davidson, K. JDavklsoni, Velain, and K. 

 Atkinsoiri, Tenison-Woods. 



In 1884 Prof. E. Deslongchamps (Etudes critiques sur des Brachiopodes nouveaux 

 ou peu connus, pp. 120-124) proposed to remove the last two species from Kraussina 

 proper, and to jolace them in a small subgenus Megerliua, on accoimt of two additional 

 short, projecting, curved, rudimentary lamellte attached to each side of the septum, under 

 the central deviating forked lamella3 characteristic of Kmusslim. Full details having 

 been given in the description of the species, it will not be necessary to repeat them here. 



