Thomson. — Additions to the Knuirhdyc of l^iatliidpdda . 45 



tliese countries of wliicli the interiors ai-e unlaiown in Liothyrella rather 

 tlian in Terebratula seuso latii. Biicknian's coarsely punctate series, how- 

 ever, must be regarded as a distinct Genetic stock. 



(3.) The Generic Position of Terebratulina davidsoni Etheridge and 



Magasella exarata Verco. 



Terehratulina davidsoiii Etheridge, an Australian Tertiary fossil, differs 

 from typical Terebraiulinae in its type of folding. The dorsal valve is 

 almost flat, but there is a faint medial sinus revealed by the course of the 

 anterior commissure. In TerebratuUna caput-serpentis, on the other hand, 

 the dorsal valve shows a fold. It becomes, therefore, a matter of consider- 

 able interest to know the type of the loop of Terebratulina davidsoni. Tate 

 (1880. p. 159) makes the following statement : " The founder of this species, 

 being unacquainted with its internal portions, placed it with a doubt in 

 the geims Terebratulina, but having seen the loop, which offers no special 

 character, I can confidently refer it to that genus." This statement does 

 not help us much, for at the time at which Tate wrote the genus Tere- 

 biatulina, was made to include such divergent loop forms as Dyscolia. wyvillei 

 and Eucalathis murraiji, while in 1886 Davidson also referred the shell 

 subsequently known as Chlidonophora incerta to Terebratulina (1). It is 

 quite possible, then, that the loop of TerebratuUna davidsoni is not that 

 of a typical Terebratuli)ia. I have endeavoured to expose the loop of some 

 specimens in the Dominion Museum from the Eiver Murray, but without 

 success, owing to the hardness of the matrix. My preparations, however, 

 reveal several important characters. In the first place, the internal margin 

 of both valves is strongly crenate, a characte]' not found in. typical Tere- 

 bratulina. There is n.o median septum on either valve, so that the loop 

 is probably short and simple as in Terebratula and Terebratulina. The 

 socket-ridges and cardinal process, however, are much stronger than in 

 typical Terebratulina, and recall those of primitive Pachyinagas and of 

 Campages. except for the absence of the bifurcating septum. The origin of 

 the crura from small processes below the inner anterior ends of the socket- 

 ridges is also distinct from the conditions in Terebratulina, where the crural 

 bases are united to the inner sides of the socket-ridges at a slightly higher 

 level. 



All these pscuUarities exist also in Magasella exarata Verco, a Recent 

 shell from South Australia of which also the loop is imperfectly known. It 

 cannot belong to any Magaselloid geniis, since it does not possess a high 

 septum, but only a low median ridge. We have, therefore, a new genus, 

 which we may designate as follows : — 



Murravia gen. no v. Genotype, Terebratulina davidsoni Etheridge. 



Plate I, fig. 4. 



Shell with incipient ventral uniplication, the dorsal valve flattened. 

 Delthyrium partially closed by two lateral deltidial plates, leaving a sub- 

 mesothyrid foramen which is margined anteriorly by the dorsal valve. 

 Surface of valves ornamented with radiating ribs, which are continued as 

 crenulations on the inner margijis of the valves. Dorsal valve without a 

 median septum, and Avith str(«ig socket-ridges and a stout pyramidal 

 cardinal process. Loop unknown, but crura springing from swollen bases 

 below the inner anterior ends of the socket-ridges. 



