Bibliographical Notice. 415 



a few of the chief features are, their absence on the 15 posterior 

 caudal vertebrae, and the upturning of the dorsal transverse pro- 

 cesses. The spinous processes, again, are rhomboidal, in contrast 

 with the battle-door shape of those of B. musculus. 



The differences of the transverse processes of the axis in the two 

 forms arc interesting. Thus the upper and lower processes unite 

 in B. musculus, forming a great common terminal plate external to 

 the ring, whereas in Megaptera the ends of the processes are three 

 inches apart. Generally the separated cervical vertebrae in Mega- 

 ptera are of less breadth compared with the height than in B. 

 musculus, and their structure would indicate more movement in the 

 former than in the latter. 



After the elaborate disquisition on the vertebra?, the author next 

 discourses on the ribs. These are thicker and more curved in 

 Megaptera, and they present a less distinct angle and external neck. 

 They moreover enclose a proportionally larger thoracic cavity than 

 in B. musculus. The sternum is narrower than in the latter, and 

 the first rib lies behind the wing of the sternum. In this example 

 of Megaptera also there was a wide oblique notch at the end of the 

 first rib, best marked on the right. 



The chevron bones are fewer than in B. musculus, and they have 

 a wider arch at the top. The spines are less developed than in B. 

 musculus. 



The last part of the treatise contains an account of the skull, 

 which is proportionally larger in Megaptera, its greater breadth 

 being especially diagnostic. It has a large foramen magnum, the 

 occipital plate of the temporal is also larger, and the temporal fossa 

 is shorter and more posterior in position. The parietal has much 

 greater expansion on the temporal fossa in Megaptera, and the 

 sphenoid does not show itself on the surface. The differences in 

 regard to the pterygoid, palate (which characteristically sends up a 

 triangular process pushing the pterygoid outwards), and the broader 

 malar in Megaptera are all carefully detailed. The characters of the 

 orbit, transverse frontal fossa, nasal bones (fitted to a triangular 

 spine of the frontals), anterior and posterior nares, ethmo-turbinals, 

 and vomer are next examined, and the differences in contrast with 

 B. musculus pointed out. In Megaptera also the mamillaries and 

 premaxillaries present a marked fall for 7 or 8 inches along the 

 beak, and they are much inclined inwards at and anterior to the 

 nasals. The deficiences of the grooves in the palatal roof further 

 distinguish Megaptera from B. musculus. The greater breadth of 

 the median beam in the former is also noteworthy, and its brain- 

 cavity is also broader ; the tympanic bone is shorter in proportion 

 to its breadth in Megaptera, and the form of the posterior division 

 of the periotic is of special interest in connexion with Dr. Gray's 

 remarks on Megaptera nova-zealandia',, the figure of the part in the 

 latter presenting a close resemblance. 



The treatise concludes with an account of the differences in the 

 mandible and hyoid in the two species. Thus the coronoid pro- 

 cess of the former is shorter, tho dental foramen is nearer the 



