LEBESCONTIA ^NIGMATICA. 201 



seeu in Fig. 11. The surface of the valves is longitudinally wrinkled and striate, 

 as in Fig. 11. 



The hinge-line is straight, and shows a thick subcylindrical body, creuulate 

 or marked with small alternately light and dark triangles. Its anterior moiety, 

 having been broken away, has left in the matrix an impression of the obhque 

 segments of this seemingly quasi-s-piva], rod-like structure, which at first sight 

 seems to be the edge of the right valve. 



In such other Dithyrocarids as figs. 1, 2, and 3 of PI. XX, figs. 1, 2, and 

 G of PI. XXIV, figs. 1, 2, 4, 6, and 9 of PI. XXV, and fig. 3 of PL XXX, we 

 find a narrow rugose hinge-plate or dorsal ridge having little or no analogy to this 

 dorsal rod-like structure in Figs. 12 a and 12 b. 



Perhaps this long, narrow, subcylindi'ical body may be the remains of the 

 straight intestinal canal, distended with food at the time of the death of the little 

 animal.^ Barrande has described and figui'ed the dorsal aspect of a specimen of 

 Trinucleiis Goldfussi with the intestinal canal open throughout its length ; and of 

 another, with the contents of the intestine indicating its whole extent, " Syst. Silur. 

 Boheme," ' Recherch. Paleont.,' vol. i, 1852, p. 629, pi. xxx, figs. 38 and 39. In 

 a Scotch specimen we have lately found an analogous structure, formed by the 

 union of narrow folds on the dorsal margins, see Fig. 14. (See Note at page 203.) 



Fig. 13. — This seems to be a much-crushed and imperfect right-hand valve of 

 a Dithyrocarid, with two raised lines, one of them apparently dorsal, and the 

 other (mesolateral) near the ventral margin, which is partly broken away, but once 

 ended with a strong spine. Another but smaller spine is present on the posterior 

 border. The anterior margin is strongly dentate, as in Fig. 11. 



As already stated, although occupying the back of the hand-specimen on which 

 Fig. 12 A is embedded, it does not appear to belong to the latter, not being exactly 

 behind it, and being flatter, and differently shaped. 



Combining the evidences given by these specimens, although they are some- 

 what obscure on account of imperfection, distortion, and embedment (Figs. 

 11 — 13), we may conclude that they are the relics of some kind of bivalved 

 or shield-like Phyllopod, near to but not identical with Dithyrocaris. 



Fig. 11 has the general contour of such a test, with some trace of anterior 

 prickles, but no posterior spines (possibly they may have been lost). Fig. 12 a, 

 differently posed, shows no prickles at its imperfect front end, but has a posterior 

 spine and a curious dorsal structure (Fig. 12 b). The longitudinal ridges, folds, and 

 striae present in all three, Figs. 11, 12, and 13, are also found in some Dithyrocarids. 



Hence it is proposed to arrange this fossil, though difficult of interpretation, 



1 It has been suggested as a possible interpretation of the cylindrical body on Fig. 12 a, and enlarged 

 in Fig. 12 b, that it may be a part of some other organism accidentally associated with the valves of 

 Lebescontia, such as a erinoid stem or a serpulite tube ; both of which kinds are found in these schists 

 (of course altered in char.acter, as such slate fossils usually are). 



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