REMARKABLE TORTOISE, TESTUDO LOVERIDGII. 511 



costal plates, which are not clear in the ribless adults. The 

 main limbs of the second, fourth, sixth, and eighth costal plates 

 are very broad, narrowly bordering the underlying rib anteriorly 

 but projecting widely beyond its posterior edge. The alter- 

 nating third, fifth, and seventh are bvit feebly developed, and 

 are very little broader than the underlying I'ib, which they cover, 

 and border narrowly and equally. This alternating ari-angement 

 of the breadth development, which takes place posterior to the 

 companioti rib, accounts for the relative widths of the lateral 

 fenestrse in the adult, in which the slender costal plates are 

 preceded by a narrow fenestra, and succeeded by one at least 

 twice as broad, the general effect being a single fenestra the 

 I shape of the epidermal shield, bridged hj a slender rib-like 

 costal. The same principle applies to the formation of the plates 

 beneath the vertebral shields. In this case the first, third, fifth, 

 and seventh neurals are well developed (progressively as already 

 noted), and form lateral sutures with the corresponding well- 

 developed heads of the corresponding costal plates. The broad 

 bridge of dermal bone thus formed is over and posterior to the 

 free underlying rib-head. This makes the segment of the median 

 fenestra immediately following, half the width of the remaining 

 segment on each side of the vei'tebrte, a similar arrangement to 

 that met with in the case of the lateral fenesti-£e. The altei'- 

 nating second, fourth, and sixth neuial plates are feebly developed, 

 barely wider than the underlying adherent vertebrjB, and are 

 widely separated from their corresponding costals, which, though 

 they are broadly developed distally, are not continued proximally. 

 The large kidney-shaped fenestia in the dei'mal bone is, however, 

 bridged by the true rib beneath ; a slight deposit of dermal bone 

 on the distal end of this rib-bridge forms the feeble, pointed apical 

 head of the costal plate which projects into the fenestras at a 

 later stage when the rib itself has absorbed. 



Thus the broad neuro-costal bridges are continuous with the 

 slender main-limbed costals, and the undeveloped neurals are con- 

 nected by the free portion of the lib with broad costal main limbs. 

 The bony bridges formed by the oblique heads of the costal plates, 

 and which separate the median from the lateral fenestrse (beneath 

 the vertebro-costal epidermal shield-sutures), are about as wide as 

 their neighbouring broad costal or neural plates. In the same 

 way narrow anterior sections of the median fenesti'te are opposite 

 the wide and posterior sections of the lateral fenestras, and vice 

 versa. 



In the young of this size there is one gi-eat difference in the 

 stage of dermal bone development, namely that of the seventh and 

 eighth costal plates. In the adult, the seventh, although narrow, 

 normally forms an uninterrupted suture with the sixth and eighth 

 from the last median fenestra to the marginal region. At the 

 present stage, the seventh is similar to the slender third and fifth 

 costals, and the eighth is similar to the broad second, fourth, and 

 sixth costals, the seventh being separated from the eighth b^ a wide 



