CAMBRIAN FOSSILS FROM PIOCHE MOUNTAINS 293 



longidactylus, that species must be taken as an example of the genus. " 

 The most important features are: "the presence around the mouth 

 of not less than ten biserial brachioles with long covering-plates 

 ('short pinnulae' of Walcott); the varying development of radiating 

 stereom-folds on some of the plates;" the disposition of the plates 

 "without apparent order, and varying in form, size, and surface 

 characters on the same body. " The specimens collected by Walcott 

 are well preserved in some parts and badly crushed in others. Those 

 in the writer's collection are in some respects very good; they do not, 

 however, show all the features noted by Walcott, but in addition they 

 possess some very interesting points not before revealed. Among 

 these are a very primitive form of stem, and highly lobate plates. 



The writer's collection of these species consists of several arms 

 (all of which show the covering-plates), some loose plates, and a very 

 beautiful specimen showing the lower part of the calyx with the stem 

 attached. The plates are considerably misplaced, and the proximal 

 part of the stem is somewhat crushed ; otherwise the specimen is in a 

 very good state of preservation. The drawing in Plate I is that of 

 a cast. 



None of the arms, with but one exception, shows the biserial nature 

 of the brachioles ; this may be due to the position from which they 

 are viewed. Walcott observed one " pinnule" to each arm plate, but 

 the writer's best-preserved specimen shows two to each plate (Fig. la). 



As noted above, the plates are described as " numerous, disposed 

 without apparent order, and varying in form, size, and surface char- 

 acters;" and further, "the margin of many of the plates appears to 

 be so indented as to have an opening or pore that passed into the 

 central cavity. " The plates in the writer's specimen are also numer- 

 ous, of varying size, and are irregularly placed, but the surface char- 

 acters described by Walcott are entirely absent. The plates are all 

 smooth and slightly concave. The marginal indentions are carried 

 so far that the plates are completely lobed (Fig. ih). At first sight 

 the lobes of the various plates appear to interlock, and thus form a 

 rather rigid connection ; but a closer examination has convinced the 

 writer that this apparent interlocking is due to the intrusion of for- 

 eign material. Some few plates, however, appear to show this con- 

 dition. It is probable that the plates were so arranged that only the 



