H. WoodTvard—On Ceratiocaris. 203 



I have hastened to give publicity to this, the earliest known 

 occurrence of a Trigonia of the recent type, that palseontologists 

 who speculate on the orgin of recent faunas may be acquainted with 

 the fact, and give figures of the specimens, that those who are 

 doubtful of their identity with a recent species, may satisfy them- 

 selves of the validity of my determination. In conclusion, I will 

 merely add that the suit'e of fossils sent to me is so extensive that, 

 when their examination is completed, I hope to be able to give a 

 more definite opinion as to the probable contemporaneity of the 

 Oolitic and recent types of Trigonia, as represented by T. semiundu- 

 lata and T. LamarcTcii. 



PLATE X.— Explanation of Figures 3-7. 



Trigonia Lamarchii, Mathn., natural size. 

 Fig. 3. — Exterior of left valve of shell. 



,, 4. — Interior of left valve. 



„ 5. — Interior of right valve. 



„ 6. — Enlarged view of the hinge. 



,, 7. — Enlarged view, showing the ornamentation of the ribs. 



lY. — On the Occukrence of Ceratiocaris in the Wenlock 

 Formation (Uppek Silurian) of England. 



By Henry "Woodward, F.G.S., F.Z.S. 

 (PLATE X., Figs. 8-10.) 



AMONG- the many beautiful fossils from the Silurian strata of 

 Bohemia, obtained by M. J. Barrande, there have been dis- 

 covered numerous detached spines, measuring from six to seven 

 inches in length, which, from their resemblance to thjs genus 

 Leptocheles of M'Coy, have received the MS. name of LeptocTieles 

 Bohemicus (Barr). 



Similar organisms fi'om the Upper Ludlow Eock, Ludlow, were 

 first described by Professor Agassiz, who determined them to be 

 fish-defences, and included them in his genus Onclms} Professor 

 M'Coy minutely distinguished them from ichthyodorulites, but sup- 

 posed them to be the slender pincers of some large crustacean.* M. 

 Barrande also recognised their true crustacean character ; but having 

 better specimens, he determined them to be the tail-spines, and not 

 the pincers, of some unknown crustacean.^ Mr. Salter, at a later 

 date, with the advantage of the materials collected by Mr. J. Slimon, 

 of Lesmahagow, showed them to be the trifid tail-spiues of Ceratio- 

 caris.^ "It is curious to see," says Mr. Salter, " how gradually we 

 have arrived at our present knowledge of its structure." 



It is now sixteen years since Professor M'Coy established the 

 genus Ceratiocaris,^ for certain bivalved Crustacea from the Upper 

 ^mian of Benson's Knot, Kendal (a fine series of which, collacted 

 by Mr. John Euthven, may now be seen in the British Museum.) 



1 Agassiz, in Miirch. Sil. Syst., p. 607. * Quart. Journ. Geol. Soc, Vol. ix., p. 13. 

 3 Salter, Quart. Journ. Geol. Soc., Vol. xii., p. 34. * Salter, Bid. 



5 M'Coy, Pal. Foss. 1850. (Four species described.) 



