PHILLIPSIA. 15 



smaller and more pointed at the tail ; convex, marginated ; the margin entire, or 

 not divided by the segments of the back. Head or thorax large, gibbous, equal in 

 breadth to the abdomen ; semicircular in front, with a broad, distinct, striated 

 margin, joining that of the body ; behind straight, separated from the back by a 

 transverse line. The surface of the head longitudinally divided into three distinct 

 parts ; the middle one of these gibbous, rounded, and, when examined under a 

 glass, apparently somewhat rough or scabrous. Between this part and the back 

 a small protuberance, constantly surmounted by a single minute point or tubercle, 

 which, however, is not visible without the assistance of a magnifier. The lateral 

 portions of the surface of the head are nearly of a triangular form ; each furnished 

 near the centre with a large lunated tubercle, discovering, in perfect specimens, a 

 reticulated structure, like that of the eyes of living insects, when magnified. The 

 back of the insect is composed of strong, convex, triarcuate segments, their 

 number varying from twenty to twenty-four, each marked with a line of very 

 minute tubercles. The middle parts of the segments are more elevated than those 

 of each side, and form collectively, down the back, a keel-shaped prominence, 

 which ends somewhat obtusely before it reaches the margin of the tail. The 

 segments of the keel directly transverse, those on each side, particularly near the 

 tail, somewhat oblique. The tail obtuse, entire, and destitute of any appendage. 



" The above-described parts are all that are ever present in the fossil. — And as 

 the under side is constantly filled with the stone which constitutes the matrix, it 

 would be impossible to examine the legs and inferior parts of the abdomen, did 

 they remain, which it is evident, however, they do not; the petrifaction being 

 formed merely from the upper shell, or covering of the back and head 



" The lunated tubercles on the head were apparently invested in the recent 

 subject with a much thinner integument than the other parts of the insect. In 

 perfect specimens the dark colour of the limestone is always seen through the 

 present sparry covering of these protuberances, while the rest of the petrifaction, 

 from the greater thickness of the crust, appears perfectly white and opaque. 

 There can scarcely be a doubt that the parts in question were the eyes in the 

 living animal. Their form, as well as the evident difference of their native 

 covering from that of the body, first led to this conclusion ; but what places the 

 matter almost beyond uncertainty is their reticulated structure. — This, with the 

 help of a glass, is sufficiently visible : and we may observe that such a structure, 

 while it proves the nature of the parts where it is found, is also illustrative of the 

 operation under which the mineral change has been effected. — Since only a slow 

 and gradual substitution of fossil for organic matter could have preserved in the 

 petrifaction a conformation thus minute." 



