EXPLANATION OF PLATES 41, 42. 847 



Figs. 72 and 73. Transverse sections through the trunk of a larva of 5*5 centims. 

 to shew the structure of the ribs and haemal arches. 



Fig. 72. Through the anterior part of the trunk. 

 Fig- 73- Through the posterior part of the trunk. 



PLATE 42. 



Figs- 74 ?6. Transverse sections through the trunk of the same larva as figs. 72 

 and 73. 



Fig. 74. Through the posterior part of the trunk (rather further back than 



% 73)- 



Fig- 75- Through the anterior part of the tail. 

 Fig. 76. Rather further back than fig. 75. 



Fig. 77. Longitudinal horizontal section through the vertebral column of a larva 

 of 1 1 centims., passing through the level of the haemal arches, and shewing the inter- 

 vertebral constriction of the notochord, the ossification of the cartilage, &c. 



Fig. 78. Transverse section through a vertebral region of the vertebral column of 

 a larva 1 1 centims. in length. 



Fig. 79. Transverse section through an intervertebral region of the same larva as 

 fig. 78. 



Fig. 80. Side view of two trunk vertebrae of an adult Lepidosteus. 

 Fig. 8 1. Front view of a trunk vertebra of adult. 



In figures 80 and 81 the red does not represent bone as in the other figures, but 

 simply the ligamentum longitudinale superius. 



