UltACHlOPODA JACKSON. 181 



too, are relatively larger, and there is a stronger development of the pedicle-collar.* 

 [n the dorsal valve the cardinaliaf differ somewhat, especially in tlie possession of a 

 definite liilolied cardinal process, which extends outwards from tlie apex of the valve as 

 a small shelf embayed medially. This feat nre. which 1 have never observed iu any 

 example of //. i>xittn<-<"ii, is present lioth in the " Terra Nova " specimens and ill two 

 examples in mv own collection from the Chatham Islands [Jackson, 1'JlG, p. 25]. 

 There is a short, low, mesial septum, which is very much stronger than that in 

 //. j^itiiii; it. In the latter species the. septum is quite rudimentary, and there is no 

 true cardinal process, the didm-tor muscles being attached directly to tin. 1 posterior 

 ends of the crural liases. //. lin-ii/it agrees with //. i^ittm;,i in this respect, except 

 that the muscular area is margined anteriorly by slight ridges. 



.Much work still remains to lie done with regard to dental plates, etc., and 

 doubtless a close study of the fossil forms of the /}///< w//\ group would reveal some 

 interesting features. Of named forms pertaining to this series the most noteworthy 

 are : Rhynchonella xtjiuintoxit, HuttonJ (Tertiaries of Australasia and Antarctica) ; 

 /?. coelata (M'Coy MS.), AVo,,ds (Tertiary of Tasmania); 7?. (?) tulmllft-ni, Tate^j 

 (Oligocene of Muddy Creek. Victoria) ; and tL'initlii/rlx inil>ri<;i(,i, Buckman|| (Tertiary 

 of Antarctica). A further study is also desirable of Rhynchonella nigricans var. 

 /'f/.ridittii (Watson. .MS.), Davidson** (Recent off the Kergueleu Isles). 



2. Lwt/ii/ivtla ]>. PI. I, figs. 1 A, B. 



llnli. Station 90 ; 100 fathoms. 



(V(.v. Two imperfect ventral valves of a Terebratulid were dredged at the above 

 station. Both examples are overgrown with Polyzoa and a pink sessile Foraminifer 

 (JPolytrema miniaceum),^\ and are so imperfect and liadly [in-served that it is difficult 

 for comparisons to be made with other forms. 



One specimen, A (PL I, fig. 1 A), is larger than the other, and seems to indicate 

 a somewhat pyriform shell, with a maximum diameter a little anterior to the middle of 

 tlie \al\e. The test is fairly thick. The posterior parl of the \alve is very convex, 

 while the anterior part is broadly flattened along the middle. The si/e of the specimen 

 represented bv this fragment is: length, 404- mm. (probably 4. r > mm.); width. :!S mm. 

 Portions of the exterior surface are covered bv verv fine, almost obsolete, radial lines, 

 and the surface generally has very prominent growth halts. The colour of the shell is 

 dirty-white. The beak, of which one side onlv is preserved, is truncated by a large. 



* See Jackson [I'JlU, pp. '_' !--'"> J and Thomson [1915 (:!), pp. 390-391, li.s,'. 1'] for descriptions and 

 figure of this feature. 



f Cardinalia embrace collectively the socket walls or rid^e- -, crural liases, hin-jr plates, and cardinal 

 process of the dorsal valve [Tliomson, 191") (3), p. :>'.'l ]. 



J [1S73 (2)]. [1877). 11 [1S'.''.I|- II [l'- )1(l |- " [1*80 and 1SS7J. 



ft I am indclited to I'mfessor S. .1. llickson, F.H.S., of the Victoria Uni\ersity. for verifying this 

 determination. 



