species of Cycachmdea from Maryland. 7 



usually simple, hut sonietiiues branchiug, witii a dein-essiou at tlu- sum- 

 mit, in the middle of whieh, when not deca3'ed, there is a terminal hud 

 of conical shape ; terminal hud, liowever, usually wantinu' in the fossils, 

 leavin.s a cavity commonly known as the "crow's nest," hy which name 

 for this reason the specimens from the Portland quarries ai-e 2>opularly 

 known. The armor consists of appendicular and reproductive organs 

 surrounding and enveloping the axis, the former being the hases of the 

 leafstalks or petioles, which are surrounded by a dense mat of ramentum 

 or fine hairs. 



The leaf stalks are normally four-sided and four-angled, the lateral 

 angles acute and nearly equal, the vertical angles obtuse l)ut unequal, the 

 lower much sharper than the uj^per, so a.s to render the cross section sub- 

 rhombic. This form varies on the one hand to a true rhomb, and on the 

 other hand to a true triangle, the most frequent intermediate type being 

 that in which the upper angle is wanting, and the two up2)er sides are re- 

 duced to a simple curve or arch, so that the cross section assumes the form 

 of a drawn bow and bowstring, the arch formed by the two up])er sides 

 representing the bow and the two lower sides, with their reentrant angle, 

 representing the bowstring. In size the leaf stalks vary from h5 to o5 

 millimeter.s in width measured between the lateral angles, and from o to 

 20 millimeters in height measured between the vertical angles, or from 

 the lower angle to the summit of the arch formed by the two upper sides. 

 The line joining the former is not generally horizontal or at right angles 

 with the axis of the trunk, but one is usually slightly lower than the 

 other. The line joining the latter is not generally vertical or pai'allel to 

 the axis of the trunk, but one is usually a little on one side of the other. 

 The only portion of the leaf bases that is always preserved in the fossil 

 state is the mat of ramentaceous hairs that surrounds them. In the great 

 majority of cases the petioles themselves are decayed to a greater or less 

 distance below the sunnuit of these mats, which thus constitute walls 

 surrounding and enclosing the j^ortion that remains of the })etioles, if any, 

 and in their absence forming definite cavities having the shape of the 

 cross section of the leaf stalks, which constitute the leaf scars. These 

 leaf scars, with or without the lower p()rti(ui of tlie leaf leases, penetrate 

 to the axis of the trunk and form a varying angle with it. Normally this 

 angle is a right angle overall the central portions of the trunk, while 

 below the organs are slightly descending and above more and more as- 

 cending to the apex, where they become vertical. At the summit, too, 

 they diminish in size and usually in form, and are reduced in and imme- 

 diately around the terminal bud to small triangular or polygonal bracts 

 {penilre of Miquel). In some species {€'. Uhleri) all the organs of the body 

 of the trunk are deflexed, and in one (C. Goucherlaiia) there is a definite 

 zone near the middle of the trunk, below which they are descending and 

 above which they are ascending. Tlie leaf scars are arranged in a more 

 or less exact quincunx order, and usually in two sets of spiral rows around 

 the trunk, in one of which they ascend from the base in the direction 

 from left to right and in the other from right to left, crossing eacii other 

 at varving angles, and both rows making a certain angle witli the axis of 



