244 a 



ACTINOCHIPvI. 



This order is established for fishes from the Upper Cretaceous of Kan- 

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

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

 family, the Pelecopteridce, so that the characters distinguishing this from 

 other orders only will be adverted to here. 



As in no other order of actinopterous fishes, there are six single and 

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

 the scapula. In Amict, there are nine such bones; but onby one of them 

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

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

 Artinopteri, there are four, three, or two basilar bones, and the anterior pec- 

 toral ray articulates immediately with the scapula. 



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

 and attached to the clavicle. 



Until other portions of the skeleton become known, it will be impossi- 

 ble to assign its place to this order, but it lessens, by its fin structure, the 

 interruption between Amia and other Physostomi. 



PELECOPTERID.E. 



A well-marked type of pectoral arch is figured on Plates XLVIII, figs. 

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

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

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

 instances I have obtained them in immediate 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 and coracoids 

 were projected forwards below. Both extremities are strongly marked with 

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

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

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

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



