44 Transactions. 



fine but irregular radial ribbing similar to tliat described by Buckman. 

 Another character which they have in common is the possession of a shorty 

 low, thin, mesia) septum in the dorsal valve, perhaps hardly strong enough 

 to be worthy of the name of septum, but sufficiently marked to leave a 

 distinct groove on well-preserved internal casts. This character is addi- 

 tional to that mentioned by Buckman as separating this series from tvpical 

 Liothynnae. Apparently, also, it serves to distinguish it from Terehrat>da. 

 for, although we are in ignorance of the internal characters of Terebratula 

 terehratula, the English Crag species, T. sjwudyJodes. T. variahilis, &c., con- 

 sidered by Buckman (1908) as probably triie Terebrattdae. possess very strong 

 and widely separated adductor muscular impressions, between and behind 

 which is a broad, raised, nearly flat platform, apparently corresponding to 

 the thin septiim mentioned above. (Plate I, fig. 5.) 



There is, moreover, a series of Recent Terebratulids comnu)nly ascribed 

 to Liothyrina which possess all the above-mentioned peculiarities. Clearly, 

 then, we are in a positioi\ to recognize a distinct genetic series. 



Liothyrella gen. nov. Genotype, Terehratula uva Broderip. 



Type of folding from non-plicate, through dorsally uniplicate, to dorsally 

 biplicate. Loop short, terebratuloid. Muscular impressions of the dorsal 

 valve separated by a thin, low, short, mesial septum. Test thin and hyaline, 

 but becoming thick and opacpie in old age, finely punctate, with grooves 

 for the reception of the pallial sinus, which are, however, only occasionally 

 visible through the shell in fossil examples. Surface ornamented with 

 a fine radial ribbing, very irregularly distributed, and absent on some 

 individuals. 



The following species may safely be included in the genus : Liothyrina 

 ■uva var. 'xotocardensis Jackson, Terehratula tateana Tenison- Woods, Wald- 

 heiritia concentrica Hutton, and a new species dredged off Tasmania by 

 the Mawson Expedition. Probably also many of the other southern species 

 ascribed to Liothijrina will be included liere, but the descriptions do not 

 state whether or not a mesial septum is present. 



Liothyrella uva has been described in great detail by Bloclimann (1908 

 and 1912) under the name of Liothyrina. He divides the Liothyrinae 

 into two groups, according to the presence or absence of certain sj^icules 

 at the base of the cirrhi (Cirrensockeln). The group in which they are 

 absent, which includes Liothyrina vitrea. occurs chiefly in the Atlantic Ocean 

 and the Mediterranean Sea, Avith the exception of one species in Japan 

 and one off Madagascar. The group in which they are present, which in- 

 cludes Liothyrella uva, is restricted to the Antarctic and South Temperate 

 seas, with the exception of one species in the Mediterranean, while L. uva 

 itself ranges from the Argentine coast, around the Horn, and up the western 

 American coast as far as the Gulf of Tehuantepec in Mexico. The spicules 

 of several species, however, are as yet unknown. It does not seem probable 

 that the presence f>r absence of these basal spicules will, taken by itself, 

 separate genetic groups, but it is quite probable that their presence will be 

 found to be a constant character of Eecent Liothyrellae.- For fossils, however, 

 this criterion cannot be used. 



In the thickness of the shell, Liothyrella .stands between Liothyrina 

 and Terebratula, while all three gen.era are finely punctate. Iii view of 

 the. known occurrence of Liothyrella in the Recent seas both of South 

 America and Tasmania, and in the Tertiaries of these countries and also of 

 New Zealand, it will be preferable to include the finely punctate fossils from 



