ANATOMY OF MEGAPTERA LONGIMANA. 79 



in affording protection from pressure after transverse processes 

 cease, or protection in the narrow part of the tail. The level- 

 ling up, or convexity, of the caudal bodies might thus be 

 regarded as the result of the passages requiring to be roofed 

 over; or the roofing-over may be owing simply to the form 

 of the bodies in adaptation to some other function. The per- 

 foration of some of the transverse processes farther forwards 

 in B. musculus and B. borealis is explained by the interruption 

 offered by the great breadth of these processes in them as 

 compared with Megaptera. 



10. Lateral Foramina on the Bodies of the Caudal 

 VERTEBRiii. — Besides the usual nutritious foramina — ranged 

 especially towards the fore and back parts of the bodies, the 

 former directed forwards, the latter backwards, here mostly the 

 size of a crow-quill or less, — there is on the caudal bodies a system 

 of larger foramina by which the roofed-over parts of the vertical 

 passage send communications laterally to the surface. Three 

 series may be recognised. They are best understood by begin- 

 ning behind. 



Only the middle series are present on the hindmost eleven 

 bodies ; on the hindmost eight, as a single aperture at the 

 middle of the side, where the body is constricted, going straight 

 into the vertical passage; on the next three (13th, 12th, 11th 

 caudal) as a pair, arranged antero-posteriorly, the communica- 

 tion having bifurcated as the bodies increased in length and 

 outwardly. This series is continued along the chevron vertebra? 

 close below the line of the transverse processes, on to the 7th. 

 The upper and lower series exist only on the 8th, 9th, and 10th 

 (the three posterior chevron vertebrae). The iqrper series, above 

 the transverse processes, the smallest, occur also as a pair, but 

 are less regular or sjonmetrical than the middle series. The 

 lower series, the largest, three, two, or one in number, pierce 

 the haemal ridges. That of the 8th is so large that it might be 

 mistaken for the passage, but the passage is continued up inside 

 the bone immediately after perforating the hsemal ridge. The 

 upper and lower series have disappeared on the 7th vertebra 

 from the unroofing of the passage. On the 6th vertebra all the 

 lateral foramina are rendered unnecessary from the shortness of 

 the passage. 



