MUSEUM OF COMPARATIVE ZOOLOGY. 223 



from right to left." The branchise of Cijamus dijfusus Dull., 

 Fig. 10, are described as " .single, cjdindrical, slender, with a 

 very short i)apilliform appendage before and behind each bran- 

 chia." They are attached to the segments as shown in Fig. U).* 

 The simple branchia is much like that observed in many sec- 

 tions of the Trilobite. Plate I. fig. 5, Plate II. figs. 2, 3. 

 Figs. 8, 8 a. An enlargement of one of the sections of Ceraurus, showing the 

 ova of the Trilobite. 



PLATE V. 



Figs. 1-3. Longitudinal sections of a C'ahjmene. Figs. 1 and 3 are cut so as to 

 intersect the legs beneath the lateral margins of the median lobe, 

 and Fig. 2 along the centre of the median lobe and between the two 

 sections showing the legs. Owing to the legs extending obliquely 

 outward, the section cuts across the first two or three joints, and 

 thus gives the peculiar pointed form. The cephalic appendages are 

 not satisfactorily preserved. One, however, in Fig. 2, is partially 

 shown. Owing to an error in the figure but seven of the twenty 

 transverse arches of the ventral membrane, beneath the median 

 lobe, are represented in figure 2. 



Fig. 4. Oblique longitudinal section crossing the median lobe. Anteriorly 

 the basal portions of the legs are seen, and then along the centre 

 the section crosses to the opposite side, cutting in its passage the 

 arches of the ventral membrane and posteriorly the a2:)pendages on 

 the other side of the median line. It combines the features seen 

 in the first three figures. The transverse arches of the ventral 

 membrane are represented too thick and large. 



Fig. 5. Lateral view of an enrolled Calijmcne. The line a, a, is the general 

 plane of the sections represented l)y Figs. 6-10, Plate I., and Fig. 

 3, b, b, of Plate III. 



Fig. 6. Front view of the same. The line a, a, corresponding to Fig. 1 ; 

 b, b, to Fig. 3 ; c, c, to Fig. 2 ; o, o, to Fig. 4, of Plate V. 



Fig. 7. A young Limulus just after hatching from the egg. (Packard.) 

 The legs are arranged as in the adult, and show the correspond- 

 ence between the cephalic appendages of Euryplcrus, Fig. 7, and 

 those restored in the Trilobite, Plate VI. 



Fig. 7. The ventral side of the head of Eurypterus remipes. (Hall.) 



PLATE VI. 

 Fig. 1. Restoration of the under or ventral surface of the animal inhabiting 

 the dorsal shell of Cabjinene senaria. In making this restoration 



• Proc. California Acad. Sci., Vol. IV. pp. 281-283, 1872. Illustrated in 

 Marine Animals and the Aiiieiican Whali- Fislu'iy, ('has. C. Scanimon, 1874. 



