hatcher: diplodocus (marsh) 36 



series Professor Osborn has estimated the number of caudals at 37. This number 

 will more than likely be increased by future discoveries through the addition of a 

 number of rod-like posterior caudals now known to obtain in the tails of certain 

 other Dinosaurs. The caudal series in Diplodocus is in length about equal to that 

 of the presacral series. The anterior caudals are short and subequal in length, 

 while posteriorly they are somewhat more elongated. The inferior blades of the 

 diapophysial laminse are broadly expanded in the anterior caudals and terminate 

 externally and superiorly in broad rugosities. These gave great surface for the 

 attachment of the powerful dorsocaudal musculature which in life must have ob- 

 tained in this region of the vertebral column and which served to facilitate both the 

 movements of the tail and the alteration of the anterior portion of the body from 

 the usual horizontal or quadrupedal position to the more erect bipedal or tripodal 

 position which was perhaps less frequently assumed during the life erf the individual. 

 The centra are invaded throughout by very deep infracentral cavities, while the 

 pleuro-central cavities are especially pronounced in the anterior caudals. All the 

 caudal centra are somewhat proccelous in contrast with the opisthocoelous centra of 

 the presacrals. The centra of all the caudals are constricted medially. The neural 

 arches are low and in the anterior caudals they are invaded by a complicated system 

 of cavities which extend down upon the superior border of the centra. Some of 

 these cavities are continued as foramina leading to the neural canal. Such doubt- 

 less served for the transmission of nerves. Commencing with the fourth caudal the 

 diapophysial laminse of this and the succeeding caudals are perforated by a number 

 of vacuities. These become elliptical in caudals five to eleven and the inner portion 

 of the inferior blades of the diapophysial laminae in these vertebrae are thus reduced 

 to a number of parallel bars, as shown in PL X. In all the anterior caudals except 

 the first the broad inferior diapophysial laminae are strongly bent forward over the 

 very deep and broad prediapophysial cavities. The postdiapophysial cavities are 

 usually reduced to one or two rather large foramina just behind and at the base of 

 the diapophysial laminse. These lead either into the neural canal or the intramural 

 cavities of the centra or neural arches. The infradiapophysial cavities are wanting, 

 and the supradiapophysial, though present, are much reduced in size. The hori- 

 zontal laminae are short and their anterior and posterior blades unite to form the 

 broad inferior blade of the diapophysial. The superior branch of the latter is 

 wanting. The pre- and postspinal and the pre- and postzygapophysial laminae are 

 all present and well developed. The latter is continued superiorly and instead of 

 merging with the median postspinal lamina as in the dorsals, about midway up the 

 spine it assumes a lateral position and is continued superiorly into an extensive, 



