12 BRITISH DEVONIAN BRACHIOPODA. 



side at the base of the deltidium, close to the hinge-line, and fitting into corresponding 

 sockets in the smaller valve. In the interior of the ventral valve a large, mesial, longi- 

 tudinal septum extends from the extremity of the beak to within a short distance of the 

 frontal margin. This plate is thick at its origin and base, but gradually decreases in width 

 while increasing in depth as it recedes from near the extremity of the beak. In the 

 smaller or dorsal valve a massive, curved, very prominent cardinal process stretches to the 

 opposite valve, where it clasps the ventral mesial septum with its forked extremity. Near 

 the base of this process in the dorsal valve a longitudinal septum arises, smaller than that 

 of the ventral valve, and divides the quadruple impression of the adductor-muscle ; the 

 socket-walls are very much expanded, forming prominent hinge-plates curving inwards 

 on each side of the cardinal process. The low r er portion of the hinge-plate supports a 

 shelly loop in the shape of two flattened stems or lamellae, which, after proceeding with a 

 slight upward curve to near the extremity of the septum, are suddenly reflected, and again 

 approach the sockets before sweeping submarginally round in the shape of a large, w r ide 

 loop, from the inner edge of which a number of smaller lamellae branch off and converge. 

 Shell-structure punctate. Dimensions variable ; some examples have attained five or six 

 inches in length by something less in width, but the generality of specimens have smaller 

 proportions. 



Obs. This very interesting and characteristic Devonian species has been the subject 

 of much investigation ; and although its internal arrangements were partially known since 

 many years, it is to Professors King and Suess that science is mainly indebted for the 

 knowledge we now possess of the calcified supports of the labial appendages. Like many 

 of its congeners, it has been shifted about from genus to genus, and has received several 

 specific denominations ; but palaeontologists have now very generally agreed to retain for 

 it the generic and single specific denomination Stringocephalus^ Burtini. 



Professor Suess, in his excellent paper, ' Zur Kenntniss des Stringocephalus Burtini,' 

 states that, if one discards the very doubtful figure in Schlotheim's ' Petrcfactenkunde ' 

 (p. 260, pi. xvi, fig. 4), it is Defrance who was the first to name and describe the 

 species. In the month of November of the same year Sowerby published a description 

 and figure of the same shell from Bradley, under the name of Tcrcbratula porrecta. 



To varieties also of this species Hoeninghaus and Goldfuss have given two catalogue- 

 names, Slrig. elongatus and Strig. striatus ; and in the ' Encyclopaedia Metropolitana ' 

 Sowerby described and figured some large, flattened, and distorted examples of String. 

 Burtini from Plymouth, under the denomination of Tcrcbratula gigantea and T. 

 Hennaltiana (see likewise ' Geol. Soc. Trans.,' 2 ser., vol. v, part 3, Explan. of plates). 



1 The etymology of Defrance's term Strygocephalus has heeu the theme of some difference in opinion. 

 Dr. Sandberger appears to have been the first palaeontologist who wrote the name Stringocephalus (in 

 Leonhard und Bronn's ' Jahrb.,' 1842). The term strix, sometimes from corruption written stryx or strux, 

 means a screech-owl {orpil, genitive orpiyyos, strivgos), and is no doubt the meaning intended by Defrance, 

 although he spelt the name erroneously. 



