ANDERSON — ON THE TILESTONES OF FORFABSHIRE. 151 
The space cleared at the Coral Den of Tealing, on the day in ques- 
tion, was about ten feet square, every patch of which contained fossil 
markings of some kind or other. The Parka decipiens* was the most 
conspicuous, colouring the whole face of the rock, a perfect Ptery- 
gotean egg-nest inclosed in its sedgy mass of vegetation. As a proof 
of the denseness of this ancient spawn-bed, in the restored ova of the 
creature, suffice it to state, that on a portion of the rock now before 
me, seven inches by five, I enumerate seventy to eighty distinct 
impressions of the egg-sac. Some flags, two to three feet square, 
had the whole surface blackened and reticulated with the eggs and 
pedicles of the oviparous organs. Tlie impressions are generally 
rounded, and of all sizes, varying from that of a garden-pea to upwards 
of an inch in diameter ; some of them, indeed, two inches by an inch 
and a half in length and breadth. The inclosing sac, in some cases, 
is entire and opaque, showing no portion of the developed eggs or 
dots ; in other cases, the vessel appears to be bursting, and part of 
the ova are visible ; while again, in others, the whole clusters are 
complete, and in their fullest development for the inspection of the 
microscopist. 
A locality so affluent in the spawn — if spawn they really be — could 
not fail to present evidences of the depositor of these curious organ- 
isms. Tracings accordingly of the huge crustacean were everywhere 
abundant. The mandibular feet, or jaw-feet, of the Pterygotus 
turned up, more or less perfect, on almost every flag. Several of the 
broad plates that envelope the body were likewise found ; as also 
some good specimens of other parts of the carapace. A large swim- 
ming-foot was among the trophies of the day. But no entire fish, 
the eager object of search, rose to the captivating beat of the hammer, 
although we trawled the identical spot where was bagged the splendid 
specimen exhibited at the Leeds meeting in September last ; and, 
* The probable relationsliips of the so-called ParTca decipiens may be — 
1. Ci>) A real fruit hke a blackbeny, as remarked by the first observers. 
2. (?) The finit of the sedges which Dr. Anderson says are so plentiful ; 
3. Cl'i) The spawn of frog-like beasts, 
4. (??) The spawn of newt-like creatures, to both of wliich Dr. Mantell has 
refen-ed. 
5. (?) The spa^vii of Pterygotus, as it is considered by Page and Salter. 
For mforniation on these points see Dr. Maiitell's paper in the Quart. Joura. 
Geolog. Soc, vol.lviii. p. 106, Lyell's "Manual of Geolog>'," Mui'chison's "Siluria," 
Page's " Advanced Texl^book of Geology," and " The Wonders of Geology" (Mr. 
Rupert Jones' edition).— En. Geol. 
