142 REVISION OF THE PELYCOSAURIA. 



transverse process is short with a very small articular face. The base of the spine is 

 thin and elongate antero-posteriorly ; it stands well forward so that the posterior 

 zygapophyses stand over the middle of the centrum. 



The second oi No. 4002 Am. Mus. (=the first of the three in No. 4015 Am. Mus.) 

 is the fourth cervical. The centrum is larger than the first; the pit on the side is 

 shorter; the transverse process is heaiy, but very short, almost rudimentary. The 

 neural arch is high and the zygapophyses stand far above the centrum with rather 

 oblique faces. The base of tlie spine in No. 4015 is nearly as large as the centrum. 

 The lowest processes are long and decurved. The top of the spine is growing large, 

 but the upper end is broken away, so the exact form is unknown. The whole spine 

 is inclined fonvard, but as the centra were placed obliquely, rising rapidly in the neck, 

 they were more nearly vertical than appears at first sight. 



The //u'rd, No. 4002 Am. Mus. (=the second No. 4015 Am. Mus.), is the fifth 

 cervical. The pit on the side of the centrum is less elongate; the transverse process is 

 short and .stands out almost straight from the vertebra. In No. 4015 the anterior edges 

 of the centrum show the irregular projection forming a face for the head of the rib. The 

 neural arch is high and the base of the spine larger than the centrum ; the first pair 

 of processes extends out 53 mm. from the side of the spine, two-fifths longer than the 

 centrum itself The top of the spine is enlarged as in the fourth cervdcal, but is 

 incomplete. 



The foiirtli of No. 4002 Am. Mus. (=the third No. 4015 Am. Mus.) is the sixth 

 cervical. The pit on the side of the centrum is smaller, the angulation of the anterior 

 edge fonning a face for the rib-head is stronger; between the third and fourth there is 

 a wide and flat intercentrum, with its upper side divided into faces for the adjacent 

 vertebrae. The corresponding vertebrae of No. 4015 has an incomplete spine, with 

 the end swollen and appearing to be flattening into a clavate form. 



Theyf/?// No. 4002 is the seventh cervical; it has the centrum rounded on the 

 bottom line, with the pits of the anterior vertebrae reduced to slight depressions. The 

 tranverse process rises from high up on the neural arch, just below the base of the 

 anterior zygapophysis, and extends almost straight out. The edge of the anterior face 

 of the centrum is bent back in a sharp angulation for the head of the rib. There are 

 well-developed centantra on the upper edge. The base of the spine is very large and 

 the first processes are longer than the centrum. 



The eighth and ninth (?) vertebrse, first dorsals. It seems probable that the two 

 vertebne described by Cope as typical of the species (plate 26, fig. i) belong next in 

 the series. They are the last with clavate apices and are probably the first dorsals. 

 The spines of the other dorsals are roughly rounded or clubbed at the end. 



In the dorsals begins the backward curve that terminates so sharply in the 

 posterior lumbars (plate 29). The succession of vertebrte posterior to the ninth is 

 rather problematical, but they have been an-anged in order by characters corresponding 

 to the vertebrae of the column of A^. microdiis. The anterior ones show the peculiar 

 forward inclination of the transverse process from the base of the anterior zygapophyses 

 characteristic of the genus. Four connected vertebrse from specimen No. 1348, field 

 number. Am. Mus., show the two posterior dorsals and the first two lumbars with ribs 

 attached. The head of the rib in the dorsals is between the centra, evidently touching 

 the end of the intercentrum and engaging the angular process on the edge of the 

 centrum. The tuberculum, reduced to a rugosity, touches the end of the short transverse 



