EXPLANATION OF PLATES 41, 43. 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 hremal arches. 



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

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



PLATE 42. 



Figs. 74 76. 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 



fig- 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 ii 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 

 % 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. 



