J;KACHIOPOD A JACKSON. 197 



socket-ridges, on the inner sides of which are large scars formed by the dorsal 

 adjustor muscles. A bilobed cardinal process is [iresent at the a]tex, and is supported 

 antcriorlv bv a bulbous prolongation into the hinge-trough. 1 have not yet fully 

 worked out the relationship of this tvpe of cardinalia, luit it is apparently Neothyroid 

 in character, and allied to that of A. lenticularis, A. OVCtlis, etc. 



10. Magellania joubini, Blochmann, 190(5. 



l<i jiiitliinl, Blochmann, Zool. Anz., 15<1. xxx, 1906, p. G97. 

 MiKii-lliiniii xiili'iitu, Smith, Nat. Hist, of National Autarct. Exped. (" Discovery"), 1901-04, 



vol. ii, Zoology, London, t907, figs. 3-4. 

 MtKjMtnia JMibini, J'.loclimann, Zeitschr. f. wiss. Zool., lid. 90, 1908, p. 009. 



I'.lochmann : Eichler, "Die Brach. der Deutsch. S.-P. Exped., 1901-03," 

 xii, Zool. iv, 1911, p. 91, pi. 42, figs. 5-6 ; pi. 43, figs. 17-18 ; pi. 44, figs. 23-2-1 . 

 Campages joulini (Blochmann): Heclley, Zool. Results, "Endeavour," 1909-1910, Sydney, 

 Dec. 1911, p. 114. 



. Stations 194, 294, 295, 314, 31 <J, 338, 339, 340, 348, 355; 140-300 

 fathoms. 



()l>*. At some of the above stations only single examples of this species \\ere 

 dredged ; at others they were more numerous. Station 339 yielded the largest 

 number. The majority of the specimens consist of immature shells. 



The shells in the young stages are milk-white and almost transparent, exhibiting 

 the muscular attachments and pallia! sinuses quite clearly through the test ; in the 

 older examples the shells arc yellowish, or horn-coloured, and the test is much thicker, 

 especially in the uniboual region. 



The largest specimen in the collection comes from Station 338. Its dimensions arc 

 as follows: Length, 38 '7; width, 2G 3 ; thickness, 27 1 mm. It is evidently a 

 gerontic individual, and is much larger than any obtained bv the " Discovery " 

 Expedition (largest = Length, 28 ; width, 23 ; thickness, 17 mm.), or by the " ({miss " 

 Expedition (largest = Length, 15 ; width, 12' 5 ; thickness, 7'5 mm.). 



The above specimen agrees almost exactly with the example figured by Smith 

 (<>!>. '//., tigs. 3-4*) under the name .17. xulaitd. Its contour is somewhat pentagonal, 

 the shell being widest about the middle. The outer surface is free from extraneous 

 growths with the exception of a few Foraminifera. On the umbonal portions the strong 

 characteristic growth-lines are moderately spaced and rounded; on the middle of the 

 valves the growth-linens are closer together, and somewhat pointed anteriorly; on the 

 outer parts they are densely crowded together anteriorly and laterally, increasing the 

 dorso- ventral diameter of the shell verv materially. 



The ventral valve is very deep, strongly arched, and slightlv longitudinally 

 carinated ; the dorsal valve is much shallower, and is flattened posteriorly. The shell 

 shows no folding. 



* Smith's figures are evidently twice enlarged. 



