AUT. 27 NEW MIDDLE CAMBRIAN FOSSILS RUEDEMANN 9 



second pairs of antennae, it is possible to assume that they may be 

 the second antennae and mandibles and that we see in the nauplius, 

 and still more so in the following protozoaean larva of the Eucarida. 

 a recapitulation of an ancestral Marrm. We can visualize our species 

 making its way through the water in a jerky or saltatory and more 

 or less irregular manner, like most of the crustaceans that have large 

 biramous swimming legs and short bodies. 



As none of the crustaceans here used for comparison, except the 

 nauplius and protozoaean stages of later crustaceans, possesses a 

 like development of the two large biramous swimming limbs, it 

 appears necessary to consider Marria not only as a member of a 

 new family, the Marriocaridae, but even of a distinct suborder of 

 the Entomostraca, the Marriocarida. 



MARRELLA SPLENDENS Walcott 



Plate 3, Figures 1. 2; Plates 6. 7 



Marrella splendens Walcott, Smithsoniau Misc. Coll., vol. 57, p. 193, pis. 25, 26, 



1912. 

 Mai-rella splendens Raymond, Mem. Connecticut Acad. Sci., vol. 7, p. 155, fig. 



32, 1920. 

 Marrella splendens Walcott, Smithsonian Misc. Coll., vol. 67, no. 4, p. 170, 1921. 



By far the most striking and bizarre crustacean discovered by 

 Walcott in the Burgess shale is Marrella splendens. In contrast to 

 its small carapace are its two pairs of massive curved hornlike ap- 

 pendages, the anterior pair of which projects sideways, and the 

 posterior pair is directed backward. Walcott placed this form with 

 the trilobites in a separate family of an unknown order, stating 

 (1912, p. 192) that this family (Marrellidae) " is less primitive than 

 the Apodidae and may be considered as near the Trilobita." This 

 determination has been challenged by some of the authors who have 

 discussed the crustaceans of the Burgess shale. Raymond (1920, 

 pp. 115-117) states: "None of the illustrations so far published 

 shows biramous appendages on the cephalon. This, coupled with 

 the presence of tactile antennae, makes its reference to the Trilobita 

 impossible, but the present interpretation indicates that it was 

 closely allied to them." Raymond places 3Iarrella with the Isopoda 

 and gives a restoration of the ventral side (fig. 32, p. 116), showing 

 two similar pairs of antennae (antennules and antennae) and three 

 pairs of simple legs (the mandibles, first and .second maxillae) on 

 the cephalon. Another authority, Fedotov (1925), also removes the 

 genus from the trilobites, considering it a typical phyllopod of the 

 order Conchostraca, very close to the Cladocera but more primitive 

 than the recent forms. K. L. Henricksen (1928), according to 

 Richter's review, arrived at the following conclusions : Marrella does 



66548—31 2 



