On a Species of Acarus, dc. By A. D. Michael. 135 
5. The conspicuous and singular tracheal system with two 
main trunks, a joint median spiracle at the symphysis of the jaws, 
and a separate lateral one on the outer side at the base of each jaw. 
6. The skin being marked with fine striae like the Sarcoptidae — 
at least on the under side. 
7. The predatory nature. 
8. The absence of apparent eyes. 
Eobin and Fumose give other characteristics, such as colour, 
&c., which appear to me to be rather specific than generic. This 
need scarcely excite surprise, even with such careful observers, when 
they state that they have only seen one species. If the distinctions 
he generic, a new genus would apparently have to he formed for 
such species as Yenustissimus. 
The Species believed to he new, which I propose to call Cheyletus 
flahellifer. 
The general and most marked characteristics of this species 
as distinguished from Eruditus are, firstly, its shorter, more 
thick-set, and powerful form, and the shorter, thicker, and more 
conical legs ; secondly, the hairs along the hack a little way within 
the edge, and most of those on the legs and palpi not being like 
the fine hairs of Eruditus, but beiog developed into fan-shaped 
expansions, each set by a short, strong, single stalk into a papilla 
in the ordinary way, but the stalk soon dividing and redividing 
into a number of radiating nervures irregularly joined by lateral 
and anastomosing nervures leaving angular spaces between, and 
similar nervures round the edge, all of which nervures are joined 
by a transparent membrane forming a somewhat fan-like expansion, 
with the radiating nervures projecting beyond the edge, and 
forming spines. These hairs have a strong resemblance to the 
leaf-like hairs of Glyciphagus palmifer, and distinguish the 
species at the first glance from all other Gheyleti of which I have 
found any record. 
The colour of the creature is semi-transparent, yellowish white, 
with a median stripe formed by the intestinal canal showing through 
the skin, but not conspicuously, much like Eruditus ; the form is a 
diamond shape, with the anterior half shortest, the front and anal 
angles of the diamond being truncated and the anal one rounded 
off, and each lateral angle being formed by a mammillary process on 
the side of the body, not quite reaching the level of the dorsal or 
ventral surface, which are much fiattened, giving the body the 
appearance of a flat cake with rounded edges. This shape is 
characteristic of the genus, but in this species the diamond is 
shorter than usual, not above one and a half times the greatest 
width, and the anal truncation is very broad. 
