790 SCIENTIFIC RECORD FOR 1885. 



A. Haswell, of Sydney, AustJ*alia, entitled " Studies on tbeElaSraobranch 

 Skeleton," That naturalist examined the coiQ]>letc skeletons or skulls 

 of 17 species of Selachians, and has described the essential peculiarities 

 of the skull, visceral arches, shoulder girdle, pectoral fins, and pelvic 

 fins, as well as dorsal, anal, and caudal. The results of his examina- 

 tions are embodied in a summary in which he recapitulates the essential 

 characters of the various families and including groups. 



Professor Haswell recognizes for the plagios tomes generally two 

 orders, the Selachoidea and the Batoidei, which are characterized as 

 follows : 



The Selachoidei are distinguished in that " in the skull the post-orbi- 

 tal processes are usually well developed ; the orbit is usually provided 

 with a cartilaginous floor formed of tlie basal plate ; there is always a 

 palato-basal articulation; the rostrum usually consists of three bars 

 with large foramina at the base. There are a series of external branch- 

 ial arches ; the first branchial arch never articulates with the skull ; 

 the hyoarch is supported by the hyo-maudibular ; the copula of the 

 hyoid has the form of a broad plate connected with its distal extremity. 

 The pectoral fin is not connected with the skull by me^ins of an ant- 

 orbital cartilage ; the ventral portion of the pectoral arch is divided in the 

 middle by a more flexible portion into two lateral halves usually slightly 

 movable on each other, and the dorsal extremities do not articulate with 

 the spinal column. The pro- and meta-pterygia of the pectoral tin are 

 never greatly elongated, and usually have the form of relatively broad 

 plates." 



The Batoidei are recognized as an order contrasted with the Sel- 

 achoidei in the following terms: "The post-orbital prociesses are small 

 or absent ; the orbit is devoid of cartilaginous floor. There is no palato- 

 basal articulation. The rostrum, when present, is usually imperforate 

 at the base. There are no external branchial arches; the first branchial 

 arch is sometimes directly connected by the hyomandibular with the 

 skull. When the hyoid arch is supported by the hyomandibular the 

 articulation takes place near the proximal extremity of the latter. The 

 ventral portion of the pectoral arch forms a continuous rigid bar ; the 

 dorsal extremities of the arch are connected either with the spinal 

 column or with one another. The pro- and meta-pterygia of the pectoral 

 fins have the form of elongated narrow bars, and the mesopterygium 

 is insignificant. The anterior portion of the pectoral fin is connected 

 by a cartilage— the ant-orbital cartilage — with the ethmoidal region of 

 the skull." 



The Selachoidei, or sharks, are disintegrated into two " suborders," 

 named Palseoselachii and l!^eoselachii. Professor Haswell considers 

 this grouping to "follow as a necessary conclusion from the researches 

 of Gegenbaur on the anatomy of the skull." The suborders are distin- 

 guished by the following characters: 



In the Palajoselachii " the occipital region of the skull is not so 

 sharply marked off from the spinal column a» in other Elasmoranchii ; 



