. Bulletin - United States National Museum. Science. MOKOGRAPH OF THE EXISTING CRINOIDS. 155 the longitudinal axis of the arm. Their component segments either are fitted closelj^ end to end, or the more proximal, sometimes all, have their angles cut away, admitting of motion in a plane parallel to the dorsoventral plane of the arm: there is no provision for lateral motion. The earlier geni- tal pinnules stand up like the oral pinnules, those of the two sides of the arm being parallel with each other, and the distal ends are always more or less curved outward toward tiie arm tips. Going outward
. Bulletin - United States National Museum. Science. MOKOGRAPH OF THE EXISTING CRINOIDS. 155 the longitudinal axis of the arm. Their component segments either are fitted closelj^ end to end, or the more proximal, sometimes all, have their angles cut away, admitting of motion in a plane parallel to the dorsoventral plane of the arm: there is no provision for lateral motion. The earlier geni- tal pinnules stand up like the oral pinnules, those of the two sides of the arm being parallel with each other, and the distal ends are always more or less curved outward toward tiie arm tips. Going outward along the arm the later genital pinnules are seen gradually to bend lat- erally outward, this being cor- related with the gradual develop- ment of a lenticular space be- tween the first and second seg- ments by which it is chiefly ox- commodated. As the genital pinnules begin to assume the character of distal pinnules their recumbenc}'' increases until the dis- tal pinnules are reached. These latter extend outward horizon- tally at right angles to the dor- soventral plane of the arm. Typically the distal pinnules consist of about 20 segments, though there may be as many as 30. They are almost always longer than, usually from half again to twice as long as, the genital pinnules, and as a rule equal the longest oral pinnules in length. They are extremely slender and delicate; the first segment is trapezoidal, the long- est side outward, or more or less crescentic, about twice as broad as long; the second is trapezoidal, the longest side inward (directed proximally). about twice as long as the first, or about twice as long as the proximal width; the third segment is squarish, or somewhat longer than broad, and the next two or three increase rapidly in length, the outer being from two to four times as long as broad terminally, usually with more or less swollen and slightly overlapping. 13—Lateiul view of ttpe specimen op Cosmiometea Please note that these images a
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