238 G. R. Girty—Triticites. 



the opaque layer, and while in some instances they reach and 

 connect with the latter, for the most part they diminish and 

 disappear before completely penetrating the translucent wall. 

 They have the same appearance whether the specimen is cut 

 lengthwise or transversely, and their cross section was probably 

 circular. In their distribution these rods or tubes seem to be 

 confined entirely to the revolving wall. Occasionally they can 

 be seen to extend part way around the turn to where the wall 

 becomes radial, but I have never seen them in the partition 

 wall itself. Fig. 5 represents a section through part of the 

 revolving wall of Triticites secalicus. The upper margin of 

 the figure is the outer margin of the wall. The dark lines 

 represent what has usually been interpreted as pores or tubes. 

 These structures can not be seen in the radial walls. 



In section, therefore, the revolving wall is seen to be barred 

 off into nearly equal stripes of opaque and translucent shades, 

 and of these it is clear that the translucent ones represent the 

 shell and the opaque ones what have been considered pores. 



Carpenter described the minute structure of " Fusulina" in 

 J 870, and his conclusions have been followed or concurred in 

 by most subsequent writers. It is interesting to note that his 

 investigations were made upon specimens from Iowa which 

 with great probability belonged not to Fusulina but to Triti- 

 cites. One can hardly doiibt that he also studied specimens of 

 real Fusulina, and it is difficult to understand why he disre- 

 garded the differences which have led me to distinguish Triti- 

 cites as a distinct group. Though he does not mention or 

 figure the dark layer which coats the walls upon their outer 

 side and which in sections defines the outline of each chamber, 

 and though other writers have not, whose work has come into 

 my hands, I am quite satisfied as to its existence and per- 

 sistence.* The interpretation of its significance, on the other 

 hand, is a matter of uncertainty. The presence and conduct 

 of this dark superficial layer and its relation to the so-called 

 tubuli have led me to entertain some doubt as to whether the 

 shell in this genus is as usually stated, perforate. 



Carpenter remarks upon the complexity of the partition 

 walls in the terminal portions of Triticites in the following 

 terms : " The irregularities which are noticeable in sections 

 made either longitudinally or traversely through the terminal 

 portions of the shell, seem explained by the disposition of the 

 alar prolongations which is revealed by fracture / for this 

 shows that the alar prolongations, as they pass to a distance 

 from the median plane, tend to interdigitate with each other, 



* Material of both Fusulina and Triticites has been examined, and from a 

 number of localities and horizons sufficient to show that these characters are 

 constantly present and are not the result of peculiar preservation. 



