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-~ Asapuus Laticostatus.* Green. Cast ns 13a) 
oy, 4 
4 re 
Cauda prelonga, pars ad marginem vix membra- 
nacea; cute coriacea, tuberculis minimis; costis latis, 
convexis et valde distinctis. 
‘The fragments of this species, which we have exa- 
mined, comprise ten articulations of the middle lobe, 
and the corresponding ribs of the sides, all in a very 
good state of preservation; the extent to which the 
* membranaceous expansion reached beyond the tail and 
the lateral lobes is very apparent, but it has been un- 
fortunately broken off all round. Our specimen ap- 
_ pears to be a natural cast of the internal part of the 
shell, or the coriaceous covering of the animal. 
The portion of this specimen of trilobite which 
still remains perfect, is two inches long, and three 
‘inches and a quarter broad. ‘The middle lobe exhi- 
bits the appearance of a very exact and gradually ta- 
pering cone, its articulations being rounded and 
slightly flattened on the top. The ribs of the lateral 
lobes are nearly straight, slightly arched, broad, 
rounded, and gradually increase in width from the 
point of their insertion; they are simple or not bifur- 
cated throughout, and are covered with very minute °. 
granulations, which are probably produced by the 
sandstone in which the animal is mineralized. The 
membranaceous expansion near the caudal termina- 
tion, is a good deal prolonged. 
The A. Laticostatus occurs in a light coloured fer- 
* From the Latin for ‘ broad ribbed.” 
