DR. T, DAVIDSON ON RECENT BRACHIOPODA. 7 



crura to the hinge-plate and not exceeding a fourth of the length of the valve, the two 

 principal stems becoming soon united anteriorly by a transverse lamella bent upwards in 

 the middle ; no mesial septum ; cardinal process small and prominent, hinge-plate 

 disunited, four diverging grooves extending from under the cardinal process to about 

 half the length of the valve, tlie central pair being the longest. In the interior of the 

 ventral valve a similar numl)er of grooves ; muscular impressions small, situated at the 

 bottom of the valve under the loop and in the rostral portion of the bottom of the ventral 

 one. Animal attached by a peduncle ; labial appendages united to each other by a 

 membrane ; brachial disk trilobed ; central lobe elongated and spirally convoluted. 

 Very delicate spicula form elegant star-like plates in the mantle. Length 1 iucli 8 

 lines, breadth 1 inch 5 Hues, deptli 1 inch. 



Hab. Abuudant in the Mediterranean iu depths of from 90 to 250 fathoms. Very 

 numerous in the Bay of Naples at depths of from 100 to 300 metres. Vigo Bay, 40 

 fathoms (M" Andrew^) . Dredged by Prof. Giglioli, during the Italian Expedition to the 

 Mediterranean in 1881, at a depth of 800 fathoms (see report in the Atti del iii. 

 Congresso Geografico Internaziouale). Also for distribution of this and other species, see 

 Jeffreys's papers " On the Mollusca of the ' Lightning ' and ' Porcupine ' Expeditions," 

 Proc. Zool. Soc. Loud. 1878, 1879, 1881, 1882. 



Ohs. Liolliyris citrea is a beautiful, well-known, and abundant Mediterranean species. 

 It varies considerably in its relative length, breadth, and degree of convexity ; some 

 specimens being quite elongated oval, 1 inch 8 lines in length by 1 inch 1 line in breadth, 

 while other examples of the same length would have a breadth of 1 inch and 3 or i< lines ; 

 some are much more pinched iu anteriorly than others, and, lastly, some are nearly 

 circular with an equal length and breadth. 



Prof. E. Deslongchamps, in bis instructive memoir on the classitication of the Tere- 

 bratulidfE, gives us the result of his studies in connection with the embryo of L. vitrea, 

 as well as of its subsequent stages of development. He states, " I have been able to 

 examine the embryo at two millimetres of size, tliat is to say from the first moments 

 when the larval condition has ended and the shell has begun to be formed ; its shape is 

 then absolutely similar to that of the young of Terehratidina ; the dorsal valve is rounded, 

 and slightly convex ; the ventral one shows a triangular hole, of which tlie summit, 

 which does not yet show any trace of a notch, will eventually become the beak. Xo 

 trace of a deltidium is to be seen on the sides of this foramen. On opening this little 

 shell, one is at once struck by the dull white of the internal walls ; and, by the aid of a 

 lens, one recognizes granulous parts affecting a certain regularity. The same dull white 

 condition is seen on the fragments of the labial appendages that have remained adhering 

 to them, hiding to some extent the brachial appendages. On examination of these frag- 

 mentary labial appendages with an enlargement of 20 to 30 diameters, one immediately 

 observes calcareous spicula, the sharp extremities of which form a most elegant border, 

 encroaching on the brachial membrane. These spicula were formed therefore from tlie 

 beginning of the formation of the shell and, already very complicated, entirely resemble 



those seen in the adult individual The cirri and the channel of the laijial 



appendages are enveloped by a layer of spicula spread out on the interbracliial 



