The chevrons are similar in form in the three North American specimens, with some differences which will be pointed out below.
Newport (male).—The first chevron consists of a pair of bones which are not united. They are longer than deep, their depth indeed being less than that of any one of the succeeding bones except the tenth and eleventh. Each presents one strong superior articulating facet. Second chevron, elongated antero-posteriorly, but not much deeper than the first. Third chevron very deep and only equaled in that respect by the fourth; narrowed and rounded off below. Fourth chevron largest and broadest (antero-posteriorly) of the series; expanded below and the lower border transverse. Fifth to eighth similar in form, but less deep successively, and the lower border more rounded. Ninth similar to eighth, but smaller and thinner. Tenth similar to first, longer (antero-posteriorly) than deep. Eleventh similar to tenth in form, but smaller.
Barnegat City (female).—First chevron bone lacking. Second like that of Newport skeleton, but smaller. Third similar to second, but much larger and more produced posteriorly; quite unlike the third in the Newport skeleton in form, and much less deep. Fourth, largest and deepest of the series; anterior and posterior borders rounded, and the inferior border similar. Fifth to eighth similar in form, but successively less deep, and all more expanded below; inferior border nearly straight. Ninth similar to eighth, but depth not exceeding breadth; lower angles produced.
Charleston (female, jr.).—The chevrons of this specimen resemble those of the Newport skeleton, but on account of immaturity they are all more or less rounded. The two sides of the first chevron are united. The second is without the posterior angular projection seen in the other specimens. The third is the deepest of the series. The eighth is not deeper than long, and hence resembles the tenth chevron of the Newport skeleton in proportion, but is, of course, much smaller. Two or three chevrons are lacking from the posterior end of the series.
RIBS.
Barnegat City (female).—First rib shortest and broadest, but considerably broader at proximal end than at distal end. Head and tubercle close together. The succeeding ribs increase in length and decrease in breadth to the fifth or sixth. The third, fourth, and fifth are expanded and flattened at distal end. Seventh, eighth, and ninth successively shorter. Distance between head and tubercle greater on second rib than on first, and on third is greater than on second. On the third to sixth, inclusive, the distance is about equal. The tubercle is scarcely distinguishable on the seventh rib, while on the eighth and ninth it is lacking, these ribs joining the transverse processes by a terminal facet only.
Newport (male).—Similar to those of the Barnegat skeleton, but first rib maintains nearly the same breadth throughout. Neck thicker than in Barnegat skeleton. Seventh rib terminates proximally in a single large rugose facet, which connects with a similar facet on side of centrum of seventh thoracic vertebra.
Charleston (female, jr.).—Similar to those of the Barnegat skeleton, but a distinct tubercle on the seventh rib. Eighth and ninth ribs end proximally in a transverse facet only, which is largest on the eighth. Tenth rib (represented by a fragment) only half as broad as the preceding ones and more nearly round in section.
STERNUM.
Barnegat City (female).—Five segments. Manubrium wider than long, convex inferiorly. Deep anterior and posterior notches, about equal, the former with an angular projection on each side. Facet for cartilaginous sternal rib thick and prominent. Second segment wider than long, about equally notched anteriorly and posteriorly, the two sides anchylosed together by a bony bridge, about as wide as the notches are deep. Third and fourth segments similar to second but smaller; similarly notched; left portion a little longer than right. Fifth segment elongated, left side very much so; the two sides joined by a narrow bridge; posterior notch very deep.