224 BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY. 



the sections described have been used, and also confirniatoiy evi- 

 dence from many other. On Plate L figs. 6-10, we have the 

 strongest evidence of the arrangement and structure of the cephalic 

 appendages. The large basal joints of the fourth or posterior pair 

 are shown in all, as also more or less of the three anterior pair. 

 If the student will take a specimen of Cahjmcne sevaria, or an allied 

 form nearly detached from the rock, and study it as he examines 

 the illustrations of the sections and restorations of that species, he 

 will see how, in cutting across such appendages as are shown in the 

 restoration, he would obtain sections like those figured on Plate I. 

 figs. 6-10. The position and form of the thoracic legs are taken 

 from such sections as represented on Plate III. fig. 9, Plate V. figs. 

 1-4, and Plate II. fig. 10, as also the confirmatory evidence of po- 

 sition in Plate II. figs. 1-3 of Ceraurus. The more cylindrical 

 character of the legs of Cahjmene as compared with tliose of Ce- 

 raurus is shown in Plate TI. fig. 10, and in Plate V. figs. 1, 3, 4. 

 The character of the appendages beneath the pygidium is not as 

 well known ; many sections show their presence as far as one, two, 

 or three joints, but beyond that their form is unknown. They 

 are restored as jointed to the end as beneath the thorax. There 

 is reason to think that some of the anterior appendages may have 

 been modified in their terminal joints, as also the posterior appen- 

 dages. Of the character of these modifications, if they existed, 

 future investigation must enlighten us. The rough appearance 

 given to the inner end of the large basal joints of the posterior 

 pair of cephalic legs is the result of an attempt of the lithographer 

 to change the form of the joints, and not designed to be so in the 

 restoration. 



Fig. 2. A transverse thoracic section of Fig. 1. In this there is given a view 

 of the structure of the thoracic appendages as they appear from a 

 study of the sections. The position of the intestinal canal, the 

 cutline of the ventral membrane or ventral surface, and the char- 

 acter and position of the appendages, with the exception of the 

 terminal joints of tlie legs, have been seen as represented. The 

 spiral bilid branchi;c and branchial arms are seen in Figs. 9 and 

 10, Plate III. There are two other forms of branchiic known in 

 Cahjmcne. One is shown in Plate III. figs. 3 and 8, and another 

 in Plate I. fig 8. 



Fig. 3. Transverse section of the thorax of Ceraurus jjleurexanthemus, to .show 

 the character of the legs. The branchia3 are not attached, al- 

 tliiiugli the sections shown by Figs. 1, 2, and 3, Plate II., would 

 fully warrant their restoration. 



Fig. 4. The jointe<l legs figured by Eichwald. 



Fig. 5. Jointed legs found on a .';Lib of liniL-stonc a.s.sociated with Trilobitic 

 remains. From Cincinnati, Ohio. 



