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PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 70 



show jagged edges, indicating that there a connecting membrane 

 was torn away. This is well shown on the anterior appendages in 

 Walcott's Plate 25, Figures 2 and 6, and Plate 26, Figures 5 and 6, 

 and for the posterior appendages in Plate 26, Figures 1 (fig. 4 and pi. 

 6, fig. 1, of this paper) and 4. 



Still more convincing is the fact that one of the specimens figured 

 by Walcott (pi. 25, fig. 3) retains, on the left side, the cheek of the 

 cephalon itself, together with the eye cavity (ventral side), which 

 shows from under the '' appendage " that has separated from the 

 test. 



Therefore, if the two pairs of appendages are placed in their nor- 

 mal position, as in the accompanying diagram (fig. 5), the margin 

 of the head of the trilobite is fully outlined. The head in })ropor- 



tion to the trunk is very 

 large — a fact that corre- 

 sponds to the supposed 

 larval age of the indi- 

 viduals — and the poste- 

 rior appendages extend 

 into the genal spines. 



The backward direction 

 of the " posterior spines 

 of the carapace " is there- 

 fore only a post-mortem 

 position of the fossils. 



(3) The antennae {a" 



in Walcott's drawings- ) 



are the same as in the 



other trilobites, as drawn 



They are like those of Neolenus sen^ratus^ 



Figure 4. — Marrella splendens. Walcott's Plate 26, 

 Figure 1. (Letters correspond to those in flg. 5) 



by Beecher and Walcott 

 even to the rows of setae. 



The so-called " mandibles " (m) of Walcott are the same as " the 

 posterior spines of the carapace," when they are in their normal hori- 

 zontal position, clearly seen in his Plate 26, Figure 5. 



The maxillulae (m') and maxillae (m'') are the four pairs of 

 longer limbs on the last segments of the carapace, and the same as in 

 Neolenus sei^atiis from the Burgess shale and other trilobites. 



This brings all " five pairs of appendages " of Marrella splendens 

 in complete agreement with the trilobites. 



(4) The " strong, small subquadrangular carapace " of Marrella 

 splendens is the compressed mass of organs, notably the stomach, 

 contained in the glabella of the trilobite. This is shown in Walcott's 

 excellent Figure 2 of Plate 25, in which the intestine is seen extend- 

 ing backward from the stomach and, where torn, exhibits the intesti- 

 nal cavitv. 



