396 Ecv. 0. Fisher — On Cleavage and Distortion. 



1 inch thick. Ceratiocaris Ludensis, H. W. (Geol. Mag. Vol. VIII. 

 1871, 104, PL 3, Fig. 3, ird of natural size), is the only British form 

 at all approaching the North- American specimen. Of this there 

 are seven body-segments and three long tapering spines (one nearly 

 9 inches long). The seven segments measure 8i inches in length, 

 and nearly 2 inches in breadth (height) as lying flattened sideways 

 in^ the slab ; six of the segments measure individually from i and 

 I- inch to 1 inch in length, and the last ( telson ? ) is 2f inches long. 

 The published figure gives a very inadequate idea of this fine 

 specimen (its carapace may have been 8 inches long) : and on a 

 visit to the Ludlow Museum lately one of us (T. R. Jones) thought 

 that there are remnants of bases of prickles on the last two segments, 

 roughly indicated on the figure referred to. The specimen will 

 soon, we trust, receive all the attention of artist and paleeoutologist 

 which it deserves. 



Some large specimens have been met with in North America also ; 

 for example, C. Deiveii, Hall, " Palasont. New York," vol. ii. p. 320, 

 pi. 71 : the one segment drawn (fig. Ic) appears to have been 

 2i inches long ; and one of the caudal spines on the same plate 

 (fig. la) is 61 inches long. 



A tail-spine from Bohemia, in the British Museum, is 5^ inches long. 

 Tail-spines of Ceratiocaris, 3 inches long, have been not un- 

 frequently found in the Lower Ludlow of Leintwardine, near 

 Ludlow. 



EXPLANATION OF PLATE XIII. 

 Fig. 1. Echifiocaris Wrightiana{T>a.-wsons-^.). Portions of abdomen (natural size) . 

 ,, Iff. Two body-segments seen from back or narrow aspect. 

 ,, \b. Another view of the lower (or posterior) of the two body-segments (seen in 



Fig. 1«) viewed from the left side. 

 From the Portage Group (Upper Erian) of Italy, New York. Collected by B. H. 

 Wright, Esq. 

 ,, 2. Three body-segments and telson, with one style and two stylets, of 

 Hchinocaris armata (Hall). Natural size. From Devonian 

 strata of the Hamilton Group, State of New York. (After 

 J. Hall.) 

 ,, 3, 4, 5. Hchinocaris sttblwvis, Whitfield, from small calcareous concretions in 

 the Erie Shales (Upper Devonian : Portage and Chemung 

 Groups), at Leroy, Lake County, Ohio. (After Whitfield.) 

 „ 3. The half of a small nodule, showing some abdominal segments and the 



inside of a valve. Natural size. 

 ,, 4. The four body-segments and telson with its spines seen in the nodule. 



Nearly twice the natural size. 

 ,, 5. A left valve. Twice the natural size. 



,, 6. Echmocaris pustulosa, Whitfield. A right valve; twice the natural size. 

 From the Upper- Devonian nodules of Leroy, as above. 



III. — On Cleavage and Distortion. 

 Ey the Rev. 0. Fishee, M.A., F.G.S. 



[Continued from p. 276.) 

 PART V. 



THE history of opinion upon the subject of cleavage seems to be 

 this. Sedgwick had come to the conclusion that cleavage was 

 a condition, " impressed on certain rocks and in certain regions by 



