72 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



Seniionotus, but did not attempt to fix its systematic position more 

 precisely. 



The reasons which in Professor De-Alessandri's opinion 

 justify a removal of this species, and with it the new genus 

 Perleidus, to the group of Catopterids, are enumerated by this 

 author as follows : " The arrangement of the cranial elements, 

 the form of the maxilla, especially its expanded posterior portion, 

 the absence of suborbital plates, and the presence of a large-sized 

 postorbital, compel an assignment of this form to the family of 

 Catopteridse, and make it necessary for us to regard it as the type 

 of a new genus. Moreover, the position and form of the fins, 

 the rather feeble fulcra, the configuration of the scales with their 

 strongly denticulated posterior border, and the absence of a 

 series of acuminate dorsal ridge-scales, are characters which 

 warrant a separation from the genus Semionotus." ^ 



The new genus Perleidus is thus diagnosed by its founder: 

 " Trunk elongate-fusiform, and head relatively small. Super- 

 ficial ornament of the cranial plates consisting of rather fine 

 tuberculations and rugae. Maxilla extended, and posteriorly en- 

 larged. A series of circumorbitals present, but no suborbitals; 

 one large postorbital plate present. Fins moderately developed, 

 comprising robust articulated rays; fulcra small. Dorsal fin 

 situated opposite the pelvic pair; caudal slightly forked. Scales 

 rhomboidal, deeper than long, smooth on their exposed portion, 

 their posterior border denticulated."^ 



That the above-mentioned genus is well characterized there 

 can be no doubt, and the reasons for excluding it from association 

 with Semionotus are sufficiently valid. It must be admitted, 

 however, that the form in question presents considerable resem- 

 blance to Pholidophorus, and the position of the dorsal fin, which 

 arises in advance of the anal, offers a marked contrast to the 

 condition observed in the family Catopteridae, from which con- 

 dition indeed is derived the name of the typical genus. We 

 prefer to accept the Milanese author's determination of the 

 family position of this genus in a provisional sense, rather than 

 to assign it elsewhere without having had opportunity to study 

 the actual specimens. 



* Studii sui Pesci Triasici della Lombardia. Mem. Soc. Ital. Set, Nai., 1910, vii, 



P- 51- 

 'Loc. cit., p. 49. 



