244 A 



ACTINOCITTIM. 



This order is established for fislies from the Ui)per Cretaceous of Kan- 

 sas and England, of wliirh nothing is certainly known excepting the scapular 

 arch and pectoral tin. These are fully described under the head of tiif only 

 family, the Pelccoplcridce, so that the characters distinguishing this fioni 

 other orders oidy will be adverted to here. 



As iu no other order of actinopterous fishes, there arc six single and 

 one paired basilar bones supporting the pectoral tin, and all articulating with 

 the scapula. In yl^^/V/, there are nine such bones; but only one of them 

 articulates with the scapula. In Batrachus, there are five, but four of wliicii 

 articulate with the scapula, and the anterior one is single. In all other 

 Actlnoplen, there are four, three, or two basilar bones, and the nntcricn- Elec- 

 toral ray articulates inunediately with the scapula. 



The clavicle is osseous, and the coracoid, if rightly deterniiued, is short, 

 and attached to the clavicle. 



Until other portions of the skeleton Ijeconie known, it will be inipossi- 

 l)lc to assign its place to this order, but it lessens, by its fin structure, tlx^ 

 interruption between Amia and other rhysostomu 



PELECOPTERID.E. 



A well-marked type of pectoral arch is iigurcd on Plates XLVIII, tigs. 

 1-2, and LIV, fig. 8. Like that of rorthcus, it supports a powerful spine, 

 but of a very dilTerent character from that genus. These spines are very 

 common in a fragmentary condition in the clay-chnlk of Kansas, and in three 

 instances I have obtained them iu immedintc connection with the scapula. 

 In one of these, the clavicles also are present. These are elongate and thin, 

 the posterior edge laminiform, the anterior obtusely rounded. The bone is 

 strongly curved antero-posteriorly, showing that the clavicles ami coracoids 

 were projected forwards below. Both extremities are strongly marj^ed with 

 grooves, the upper for sutural union with the posttemporal, and perhaps 

 epiclavicle. One eiul is wider than the other, and its posterior edge is like a 

 convex knife-blade. The scapula is quite massive; the general form of ils 

 IkkIv being that of a very irregular three-sided pyramid (see fig. 9). its 



