miACHIOPODA JACKSON. 195 



in its larger sixe, fewer punche per square millimetre, and, to some extent, in its 

 spiculation. In addition to the Ion-going, L. /</</////<////// is easily distinguished in mi 

 L. antarctica, as well as from L. urn from the Magellanic region, by the peculiar 

 disposition \' the braehidium. This is of the L, x////r///</iv type, with parallel 

 descending liranehes and short, broad, (i-ansverse hand, while in L. nt<ir<-tn;i and 

 L. um the liranehes diverge and the transverse hand is long and narrow in L. urn it 

 is longer perhaps than in any other recent species. A full discussion of these points 

 is given in my paper in the (,','n/ni/irnl .}f<i : /,i;///>' for Felirnary, 19 L8. 



9. Magellania fragilis, Smith, 11)07. 



Maiji-lliiiu'afriKjlllx, Smith, Nat. Hist, of National Antart-t. Kxj>od. ("Discovery"), 1901-01, 



vol. ii, Zool., London, 1907, p. 1, figs. 1-2. 

 MiKji'Uau'ui frnijlliK, Smith : Eichler, "Die Bracli. der Deutsch. S.-P. Exped.j 1901-03,'' xii, 



Zool. iv, 1911, p. 93. 



Stations 31G, 338, 339, and 355 ; 140-300 fathoms. 



K. This species was first made known to science in 1907 by the late Edgar A. 

 Smith (oft. <//.), who founded the species on a small numlier of more or less damaged 

 specimens obtained hy the " Discovery " Expedition at Agassix Island, 300 fathoms, 

 mud, off the ice-barrier. Smith, however, only gives external views of the species, and 

 his description of the internal features is somewhat incomplete ; details of the cardinalia 

 and the numlier of punctse per square millimetre being wanting. 



The specimens obtained by the "Terra Nova" Expedition at the above four 

 stations are few in number. They are not so large as the "Discovery" examples, but 

 appear to possess the characters of this species. A few of the examples from Station 

 355 are curiously malformed and notched around the periphery, caused through some 

 injury to the mantle during growth. 



Through the kindness of the British Museum authorities I have had the loan of 

 one of the original specimens upon which the species was founded by Smith, and in the 

 following pages I have added certain details concerning this example, as it shows more 

 adult features than any of the "Terra Nova "specimens. 



In general outline the "Discovery" specimen (38x30 "3 mm.) is almost pen- 

 ta"onal with a truncated front. The early stages, however, as demonstrated bv the 



J O 



growth-lines on the shell, show it to have been rounded durhif the neanic and early 



O O / 



ephebic periods of growth. This is confirmed by the "Terra Nova" examples. It 

 possesses moderate growth-lines, which are well spaced over the major portion of the 

 shell, but are somewhat crowded together at the anterior and lateral margins. The 

 shell appears to be lenticular as regards type of folding, but there is some slight 

 indication of incipient ventral nniplication. 



The beak, which possesses very much subdued ridges, is truncated by a rather 

 large circular foramen, bordered anteriorly by conjoined deltidial plates. The foramen 

 is situated almost entirely behind the ridges, and i-; then-fore permesothyrid in 



