BY A. II. S. LUCAS AND C FKOST. 283 



Museum, we have come to the conclusion that our specimens 

 described from the St. Clair Lake, Tasmania, in theP.L.S.lST.S.W. 

 1893, p. 227, as neniisphce7'indoii tasmanicuin, are only among the 

 numerous varieties of //omohpida canuarince, D. & B. Our chief 

 reason for including the apparently new species under the genus 

 f/fmisphceriodou was the relatively large size of one of the teeth 

 in each side of each jaAv. 



The genus Hemisphceriodon was separated off from Hinulia in 

 1867 by Peters. It is still considered, and we think rightly, as 

 distinct from Ijygosoma, in which Hirudin and Uomolepida, with 

 others, are included by Boulenger (B.M.C.) 



The synonymy of Homolepida casimrince, D. & B., then consists 

 of OmolepidAa casuarinm, Gray, Cyclodus casiiarince, Dum. et 

 Bibr., dJomoIejnda nigricans, Peters, 1874, Lygosoma muelferi, 

 Peters, 1878, and Hernis/dueriodon iasma>ticum, L. & F., 1891. 

 / femisphcBriodon is separated from tJoni<depida thus : 

 In Hemisphceriodon (1) the pterygoid bones are sepai'ated on 

 the median line of the palate, the palatal notch extending 

 anteriorly to an imaginary line connecting the centre of the eyes; 

 (2) lateral teeth with rounded crowns, one on each side of each 

 jaw enormous, the others small. 



In Homolepida (Omolepiduta) (1) the pterygoids are usually in 

 contact anteriorly, the palatal notch not extending forwards to 

 beyond the centre of the eyes; (2) the maxillary teeth conical or 

 obtuse, subequal. 



In H. tasmanicum (castiarina'J (1) the palatal notch extends 

 forward to the hind border of the eye; (2) lateral teeth with 

 rounded crowns, one on each side of each jaw much larger than the 

 others, relatively as much larger as in young //. gerrardii. Thus 

 this species may be claimed on the first ground by Homolepida 

 (Lygosoma), and on the second ground by Hemisphceriodon. 

 Large individuals approach H. gerrardii to some extent also in 

 habit. On the whole, pending a more satisfactory classification 

 of the subgenei'a of Lygosoma, it is probablj' best to leave this 

 variable form under the designation Lygosoma (Homolepida) 

 cosnarince. 



