258 Messrs. R. B. Newton and R. Holland on some 



"en losange," as Dr. Verbeek has already pointed out merely 

 from an examination of fig. 1 c in Brady's plate ; and tliey 

 arc therefore properly to be referred to the subgenus " Lepido- 

 ct/clino,^^ which is characterized by the possession of non- 

 rectangular ciiambers in the median plane. 



In order to clear up as far as may be the proper relation- 

 ships of Brady's species we have carefully examined the 

 numerous free specimens, now in the Britisli ]\Iuseuin, which 

 Dr. Brady had before him when writing his paper; and by 

 the kindness of Dr. Harmer, of the University Museum of 

 Zoology at Cambridge, we have been enabled thoroughly to 

 examine the actual figured and other prepared specimens 

 used by Brady to illustrate his paper. 



We have no hesitation in saying that Brady's Sumatran 

 specimens are identical with a species which occurs frequently 

 in our slides cut from one of the pebbles taken from the bed 

 of the River Malinam ; and we agree with Dr. Verbeek that 

 they are identical also with the species g and k figured in 

 plate xi. of his work already several times referred to. 



So far as we can see the specimens fall under no species 

 already described — and here we are in agreement with 

 Dr. Verbeek — and we therefore describe it as a new species 

 under the designation Orbitoi'des {LepidocycUna) Verheeki. 

 As the Sumatran specimens which we have been able to 

 study are perfect, numerous, and quite free from matrix, we 

 have preferred to figure for the most part preparations of 

 those rather than our Bornean sections. Fig. 9 of PI. IX., 

 however, is from one of our slides. 



Characters. The species is dimorphic — that is to say, some 

 individuals have the initial chamber large, while in otliers it 

 is very small, practically invisible. They are distinguished 

 here as form A and form B respectively. 



Form A. — Shell discoidal, regularly swollen at tlie centre ; 

 surface smooth and devoid of ornament ; edge very slightly 

 thickened and rounded ; initial chamber large and apparently 

 always succeeded by a chamber still larger and partly em- 

 bracing the first ; chambers of the median plane lozenge- 

 shaped, the chamber-walls being slightly curved ; chambers 

 above and below the median ])lane irregular in shape, but 

 somewhat regularly disposed. External dimensions of shell 

 5 to 6 millim. in width by 1*5 to 2 millim. in thickness; 

 inside dimensions of the two central chambers taken together 

 about '5 millim. in width by "25 millim. in dej)tli ; chambers 

 of median plane very minute; long axis of lozenge about 

 •09 millim. 



The external appearance of a typical specimen is well 



