Correspondence—D. MW. S. Watson. 381 
Sulphide. Crystals of this rare substance have recently been prepared 
by Mr. F. P. Burt, University College, London, by sublimation. The 
constants obtained were a:5:¢=0'8879 : 10-8480 : B=90° 23’, and 
the observed forms were (100), (010), (001), (110), (101), (011), 
(101), (210), (111), (121), the last four being new. The crystals 
were invariably oniees ae by polysynthetic twinning about 
(101). <A biaxial interference figure with strong positive double 
refraction was visible through (101). —Dr. G. T. Prior and Dr. G. F. H. 
Smith: On a new Arsenate-and Phosphate of Lime and Strontia from 
the Indian Manganese Deposits. Chemical analysis showed that the 
mineral approximates to the arsenic analogue of apatite. The crystals 
were not well formed, but the physical characters as far as they could 
be determined accord with those of apatite. The name fermorite, 
after Dr. L. L. Fermor, of the Geological Survey of India, who has 
made an exhaustive study of the manganese deposits, is proposed for 
this analogue. The presence of strontium, which has not yet been 
detected in apatite, is of interest.—L. J. Spencer: A (fifth) List of 
New Mineral Names. 
CORRESPONDENCE. 
A CHELONIAN FROM THE PURBECK OF SWANAGE, DORSET. 
Sir,—In my article on the above subject (see Guon. Mae. for July, 
pp. 311-14) the following note was sent in too late for insertion :— 
Hooley’s Plestochelys vectensis from the Wealden of the Isle of 
Wight (Guor. Mae., 1900, p. 263) shows a preeneural and seven 
neurals, instead of eight neurals as suggested in the original 
description. The specimen probably indicates a new genus. 
Seeley’s Pleurosternum typocardium, which was _ insufficiently 
characterized in his Index to Aves, etc., in the Cambridge Museum, 
is founded on a specimen of Glyptops ruetimeyert. It is much 
more oval in outline than my Fig. 1, a difference possibly partly 
due to sex, but otherwise shows no new features. The protuberances 
caused by the crushing through of the axillary and inguinal buttresses 
are quite evident. Seeley’s other species, Pleurosternum sedgwichit, 
vansittardi, and owent, appear to be typical examples of P. budlocki. 
D. M. 8. Watson. 
Victornta UNIvERsITY, MANCHESTER. 
THE TERM ‘LATERITE’. 
Srr,—I refuse to plead guilty to the charge advanced by Mr. Scrivenor- 
in your July issue of attempting to force a new definition of laterite 
on geologists and engineers. I only ask that the word shall be 
employed for rocks which are chemically and physically allied to 
that on which it was bestowed by Buchanan. 
‘In dealing with questions of priority of nomenclature we must 
inquire what was the thing (rock, mineral, or organism, as the case 
may be) to which the name was first applied, not why it was so 
applhed. Buchanan found a rock widely extended in India which was 
unlike anything with which he was familiar, and he thought that it 
