A NEW TYPE OF TELEOSTEAN CARTILAGINOUS PECTORAL GIRDLE. 505 



On a new Type o£ Teleostean Cartilaginous Pectoral Girdle found in young 

 Clupeids. By E. S. Goodrich, F.R.S., Sec.L.S., Prof, of Comparative 

 Embryology in the University of Oxford. 



(With 6 Text-figures.) 

 [Read 18th November, 1920.] 



While examining some thionin preparations of the cartilaginous skeleton of 

 a young sprat, Clupea sprattus, caught at Plymouth *, I found that the 

 pectoral girdle presented a quite unexpected structure, which seems to have 

 hitherto escaped the notice of anatomists. On investigating the young of 

 Clupea harengus and C. jnlcliardus the same peculi.fr form of girdle was 

 found, and it may be considered as typical of the genus Clupea, and possibly 

 may be found to occur in related genera. 



In all living Teleostei the endoskeletal girdle, preformed in cartilage in 

 the young, is in a reduced condition relatively to that of the large dermal 

 bones which support it, and consists of right and left halves usually clearly 

 separated in the middle line. Each half is firmly fixed to the cleithrum, and 

 is formed of a short dorsal scapular region and of a generally much larger 

 ventral coracoid region. These are separately ossified, and in many lower 

 Teleostei, including the Olupeiformes, there is another ossification in a dorsal 

 mesocoracoid arch, forming an inner buttress to strengthen the girdle near 

 the articulation of the fin. 



Although in many Teleosts the coracoids may be quite large, and may 

 extend towards the middle line and meet, ventrally, yet, so far as I know 

 the left and right halves are always said to remain separate (3). Neither in 

 the well-known monographs of Parker (5) and Gegenbaur (2), nor in the 

 works of Stannius (6) and other authors, is there any mention of a median 

 fusion of either cartilage or bone (the only possible exception I have met is 

 that of two little ventral epicoracoid cartilages, widely separated from the 

 coracoids, described by Parker as partially fused (5)). On the other hand, it 

 is a familiar fact that in the Elasmobranchii and Dipnoi the two halves of 

 the cartilaginous pectoral girdle, originally separate in the embryo, usually 

 become firmly fused below the pericardium (3j. 



In the young Sprat, Herring, and Pilchard about 20 to 30 mm. in length, 

 the endoskeletal pectoral girdle is in the form of a solid transverse bar of 



* I am indebted to Miss Lebour for all the material on which this study is founded and 

 have to thank her for placing it at my disposal. The specimens were preserved in formol. 

 LINN. JOURN. — ZOOLOGY, VOL. XXXIV. 37 



