NO. 2 MIDDLE CAMBRIAN HOLOTHURIANS AND MEDUSA 53 



Genus LOUISELLA, new genus 



Elongate, cylindrical body tapering toward the anterior and poster- 

 ior ends. Flattened on the ventral surface. With numerous tube feet 

 or podia in two longitudinal rows, and what may be papillae on two 

 peltate extensions at the posterior end. Mouth and anus unknown 

 but probably terminal. 



Genotype. — Loiiisella pednncnlata, new species. 



The stratigraphic range and geographic distribution are the same 

 as for Laggania (p. 52). 



LOUISELLA PEDUNCULATA, new species 

 Plate 13, fig. 4. 



Only one specimen of this species is known. The main outlines 

 of its description have been given under the genus. Although the 

 specimen is flattened in the rock the ventral sole is beautifully out- 

 lined by the marginal row of podia on each side. This probably re- 

 sults from the thickening of the body wall along the ventral side. 



The two peltate extensions at the posterior end suggest very 

 strongly the presence of numerous papillae along their margins as 

 in the recent Scotoplanes insignis Theel.* A somewhat similar but 

 obscure fringe occurs at the anterior end which may indicate ten- 

 tacles or papillse. 



Formation and locality.- — ^Middle Cambrian: (35k) Burgess shale 

 of the Stephen formation ; west slope of ridge between Mount Field 

 and Wapta Peak, one mile northeast of Burgess Pass, above Field 

 on the Canadian Pacific Railway, British Columbia, Canada. 



Family SYNAPTID^- 



Body cylindrical and elongated. Mouth and anus terminal. Cal- 

 careous ring surrounding the oesophagus. Tentacles pennate or 

 digitate. Without podia or radial canals. 



The above outline describes the family as far as it is necessary to 

 include all that is known of Mackenzia costalis within it. Future 

 discoveries may afford data by which to draw it closer to this family, 

 or to remove it to a new one, probably the latter. At present nothing 

 is known of spicules in the Cambrian species. 



^Voyage of H. M. S. Challenger, Zoology, Vol. 4, Holothurioidea I, pi. 7, 

 figs. 1-3. 



^ See Treatise of Zoology, by E. Ray Lankester ; pt. 3, p. 234, for definition 

 of family. 



