Fig. 1 Cross section through the posterior part of the otic region of an embryo 

 having a carapace length of 11 mm. The section is slightly oblique, the left side 

 (reader's) being anterior to the right side. X 15. 



Fig. 2 Cross section through the posterior part of the otic region of the same 

 embryo as figure 1, and slightly anterior to it. On the right side the fissura meto- 

 tica (/.m.) and sulcus supracristularis (s.s.) are shown and on the left side the cana- 

 lis perilymphaticus opens into the cranial cavity by the extreme anterior end of 

 the fissura metotioa. X 15. 



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