12 AUSTRALASIAN ANTARCTIC EXPEDITION. 
“a 
recent rhynconellid which shows a tendency to folding of the Cincta type, but which 
also differs from Frieleia halli by a separation of the crura or hinge-plates clear to the 
cardinal margin. The differences separating these two species from Hemithyris seem as 
important as those separating them from Frieleia, and they may be provisionally referred 
to as the Rhynconella cornea series. With this series R. racovitzae can have little 
relationship, and its dorsal uniplication is in accord with its reference to Hemithyris. 
Rhynconella gerlachei is a shell in the lenticular stage, so that its type of folding 
gives no clue to its generic position. The cardinalia, however, are not of the Hemithyrid 
pattern, but present considerable resemblance to those of Frieleia, to which genus it 
may be provisionally referred until adult examples are discovered. 
The fragments described by Jackson under the heading of Hemithyris sp. consist 
only of the posterior parts of valves, and consequently the type of folding is not known. 
From the other characters it seems probable that they belong to a new species of 
Hemithyris with the long beak which separates the H. psittacea series from the short- 
beaked H. nigricans series. A fossil member of the H. psittacea series, H. antarctica, 
has been described by Buckman (1910) from the Post-Tertiary Pecten Conglomerate 
of Cockburn Island, off Graham Land, and Jackson states that his specimens present 
some points of resemblance to this species. 
The present species, Hemithyris striata, is an adult shell in the lenticular stage, 
and, as the dorsal valve is unknown, some uncertainty as to whether it belongs to Hemi- 
thyris or Frieleia must remain. It is not impossible, as far as shape and ornament are 
concerned, that it is the adult form of Frieleia gerlachei. It possesses the short beak 
of the Hemithyris nigricans series, but differs from these species (H. nigricans, H. 
pyxidata, H. doederleini) by the fineness of the radial ornament, as well as by the lack of 
folding. It is easily distinguished from Hemithyris racovitzae by its rounder shape 
and relatively lesser convexity as well as by the absence of folding. The only other 
southern species of rhynconellid not discussed above is the Australian form, Hemithyris 
colurnus Hedley, which, from characters of beak and cardinalia, must be referred to 
Aetheia, and therefore need not be further compared with our species. 
SuPeRFAMILY THREBRATULACKA Waagen. 
Family TEREBRATULIDAE Gray. 
Genus LIOTHYRELLA Thomson, 1916. 
Genotype 'TEREBRATULA UVA Broderip. 
Liothyrella was founded to include a series of finely punctate recent and Tertiary 
terebratulids distinguished from Liothyrina and Terebratula by the possession of a low 
but sharp median septum in the dorsal valve, accompanied in many cases by an 
irregularly distributed fine radial ornament, All the known species, L. uva, L, notor- 
