470 fteports and Proceedings. 
phim. Although so unlike them in the form of their shelly cover- 
ing and long body, Prof. Hall and others have shown the close 
relationship which exists between Pterygotus and Limulus (the 
King-crab) of the present day. 
The Xiphosura have succeeded the Eurypterida, and held their 
own from the Coal-measures to modern times, occurring in the 
Oolites of Germany so like the recent forms as not to be dis- 
tinguished from them generically. 
Some may, perhaps, be surprised to find the group known as 
the Cirripedia (which is represented by the ‘ Barnacle’ and ‘ Acorn- 
shell’) placed with the Crustacea; but Profs. Hancock, AJlman, 
Thompson, and Dr. Darwin have shown them to be true Crustacea, 
which, when young, rove freely through the sea, but, when they 
arrive at their final condition, become attached to foreign bodies, as 
wood, ships, rocks, &e: &c,, and there pass the remainder of their 
days in a sessile or pedunculated shell. 
TURRILEPAS WRIGHTUO, H. Woodw. (Chiton Wrightii, De Kon.) 
Fig. 1. Specimen from Mr. E. J. Hollier’s collection. 
Fig. 2. 6 Mr. Charles Ketley’s  ,, 
Fig. 3. eae Mr.:H. Johnson’s iy 
Figs a, b,c, represent the three forms of plates of which the several rows are composed in 
figs. 1-8, which bear the corresponding letters. ‘The opercular valves are not known. 
Until June 1865, the oldest Cirripede known was the Pollicipes 
Rheticus, from the Rhetice beds of Somersetshire ; but the author 
has just described* a new pedunculated Cirripede, with intersect- 
ing rows of plates (similar to Loricula), from the Wenlock Lime- 
-stone and Shale (Upper Silurian) of Dudley, figures of which are 
given above.t 
The Decapods (Crabs and Lobsters) date’ back their ancestry, 
the former to the Ooltte, and the latter to the Coal formation. 
This group contains among its members those most highly organ- 
ized genera, the land and semi-aquatic Crabs, whose gills (enclosed 
within the shell) are so beautifully defended from evaporation, that 
* See Quart. Journ. Geol. Soc., vol. xxi. part iy. 
+ Two detached valves of this fossil were discovered by Mr. John Gray of 
Hagley, and described as a Chiton by M. De Koninck, Bulletins de Acad. de 
Bruxelles, 1857, 2nd series, vol, iii. p. 199, pl. 1, f. 2. 
