296 S. H. SCUDDER OX NEW TYPES 



say are much better preserved, and winch for the first time they discover to have longi- 

 tudinal markings. 



A carefnl study of the four specimens seen by me show that there is no variation in 

 the character of the rods in different individuals beyond what is found on one and the 

 same individual; and these may now have a particular description, which from their 

 remarkable structure they well merit. 



The rods (pi. 26, fig. 1) are straight, rigid, needle-shaped bodies. 5-0. 5 mm. long and 

 about 0.07-3 mm. in diameter, imperceptibly tapering, so as to be at tip fully three-quarters 

 as large as at base, and terminating abruptly, apparently with a broadly rounded tip. It 

 seems to be composed (pi. 2G, figs. 2, 4) of an inner core, about nineteen-twentieths (in 

 diameter) of the whole, and a shell upon which very delicate markings are traced; the 

 shell readily peels from the central core and may thus lie mounted in balsam and examined 

 by transmitted light under the microscope (pi. 20, fig. 3), when the distinctions between 

 the parts may be readily seen. 



Two schematic drawings are given to show the minute markings of the shell. PL 26, 

 fig. 4, represents a diagrammatic view of the cross section of a rod, magnified 1000 diame- 

 ters, and tig. 2 represents an oblique view or. the same scale. The rods arc thus seen to 

 be longitudinally furnished with about eighteen mainridges. as straight as the rod itself, 

 equidistant from each other, rounded at the top and with steeply sloping sides so as to be 

 scarcely broader at base than in the middle and of equal basal breadth and height; these 

 ridges arc divided at subequal distances by notches, or rather they are made up of serra- 

 tions, the highest end of the serration next the tip of the spine ; the greatest increment in 

 the height of the serration is in its basal fourth, calling the base the end toward the base 

 of the spine ; and the extreme height is about double the least height; in the same basal 

 fourth occurs the greatest increment in breadth, for each serration increases also in this 

 dimension toward its highest point, so as to be about one-fifth broader at apex than at 

 base. To increase the distinction of the serration, there appears at the base of each to be 

 a closed joint, separating each one from its neighbors. Although at first these serrations 

 appear to be divided off from each other with remarkable regularity, and at a distance 

 apart averaging about .0133 mm., a little observation shows that this is not strictly true; 

 and a measurement of nineteen successive serrations on the same ridge showed the follow- 

 in- series as given in millimeters: .0144. .0135, .0182, .0144, .0133, .0115, .0154, .0115, 

 .0173, .0135, .0135, .0115, .0144. .0135, .0125, .0115, .0077, .0115, X135; another shorter 

 set on another spine gave the following series: .0154, .0115, .0154, .0102, .0135, making 

 the average a very little less. 



Between every pair of these ridges are generally three, sometimes two, exactly similar 

 but miniature ridges about one-eighth the height of the others, anil also cf equal height 

 anil width but apparently a little more triangular in cross section ; these likewise are 

 broken up with serrations, apparently resembling the others closely but so minute that the 

 proportions cannot be so closely studied as to be quite sure of this ; they certainly differ 

 in that the serrations arc proportionally longer, there being but two or three to each ser- 

 ration of the larger ridges, as shown in pi. 20, fig. 2. In this drawing, based on instruction 

 given the artist from my studies of numerous fragments, and by his examination of the 

 specimen represented in pi. 26, fig. 3, he has misunderstood a single point, in bringing the 



