242 NEW YORK STATE MUSEUM 



that they are subtegminal food grooves and believe with Barrande 

 that the structures are respiratory in their nature. 



Endothecal structures. An examination of plate 6, figures 

 I and 2, will reveal another reason for the difficulty heretofore 

 found in determining the position of the sutures bounding RA. 

 The undercutting of the specimen to remove it from its bed removed 

 also so much of RA and X as to carry away nearly all of the com- 

 mon sutural edges of these plates. This suture was 2.8 mm 

 long, but all that remains of it is .25 mm next to r.post.R 

 and about the same next to post.B. It could not be seen because 

 nearly five-sixths of it had been removed. The cutting had not only 

 carried away nearly all of the surface of these plates but it had also 

 penetrated beneath the plates and exposed a little over four square 

 millimeters of the interior. This area, the greater part of which is 

 immediately under the stereom of x, is of peculiar interest for it 

 displays markings in carbonized lines which appear like sections of 

 a network of tubes having a diameter of about 0.2 mm. When 

 first noticed, it appeared as if we had here the remains of a colony 

 of Bryozoa but so soon as it was discovered that these structures 

 were not on the surface of the plates, but beneath them, they received 

 more careful examination. 



In plate 6, figure 3, we have marked a sutural canal c and at the 

 extreme right-hand side of the figure there is a broken piece of 

 r.post.R with an angle of the crystalline calcite resting on the su- 

 ture. This angle, which is marked d, may be seen in all four figures. 

 If now on figure i of this plate we place a millimeter rule tan- 

 gent to the under surface of the sutural canal designated as c and 

 let the edge of the rule run by the lower angle of the broken calcite 

 designated as point d, we shall have a line 58 mm long which 

 will afford us a good basis for study and comparison of the figures. 

 Resting on this line and 28 mm out from the sutural canal c 

 we find a dark triangular area with a base of 2 mm. Below 

 this are three parallel tube sections which together occupy a width of 

 6 mm. Tubes also lie against the other two sides of the tri- 

 angle, but a series parallel to these is not detected. The tube sec- 

 tions here display rounded ends showing the sections to be in part 

 longitudinal and in part tangential. In other words, the tubes were 

 curved. Outside of this area the sections approach more closely 

 the character of circles and it is apparent that we are here dealing 



