7?. M. Bry done— Chalk Polyzoa. 153 



0. armatus (Owen). Dorsal vertebrae with lateral pits; sacral 

 vertebrae not much abbreviated. Ratio between humerus and 

 femur 4 : 5. Articular ends of femur not much expanded. 



0. Lennieri (Nopcsa). Dorsal vertebrae without lateral pits; 

 sacrals strongly abbreviated. Fourth trochanter feeble but well 

 marked. Articular ends of femur not much expanded. 



0. vetustus (Huene). Articular euds of femur moderately expanded, 

 without fourth trochanter. 



Genus Stegosaurus (Marsh). Ilium very elongate anteriorly, its 

 breadth increasing only gradually backwards. Four sacral ribs 

 present. ISTo very great dorso-ventral compression of the sacrum. 

 Articular ends of femur not expanded. 



St. durohrivensis (Hulke). Femur with strong fourth trochanter. 



St. prisons (Nopcsa). Neural arches of dorsal vertebrae moderately 

 elevated. Femur with rudiment of fourth trochanter. Ratio of 

 humerus to femur 5 : 9. 



St. ungulatus (Marsh). Neural arches of dorsal vertebrae very 

 much elevated ; sacrals not much abbreviated. Femur without fourth 

 trochanter. Ratio of humerus to femur 1 : 2*3. 



II. NOTES ON NEW OR IMPERFECTLY KNOWN CHALK PoLYZOA. 



By E. M. Brydone, F.G.S. 



{Continued from Decade V, Vol. VII, p. 483, 1910.) 



(PLATES IX AND X.) 



Pavolunulites scandens, sp. nov. PI. IX, Figs. 1-4. 



Zoarium free, unilaminate, the back divided by somewhat wavy, 

 shallow, slightly diverging furrows into long narrow strips which 

 correspond with the lines of zooecia; these strips are occasionally 

 crossed by very shallow depressions or furrows corresponding to the 

 boundaries of individual zooecia. 



Zooecia disposed in gently diverging and outward-curving lines, 

 which are in some places confluent and in others separated by 

 vibracularia ; they are short and broad, with bulging sides, but 

 very variable in size and outline, average length , 55--6 mm., breadth 

 (maximum) - 6 mm. ; the back wall very soon leaves the back of the 

 zoarium and rises gently but steadily up to the level of the front 

 wall at the head of the zooecium, and the succeeding zooecium 

 groAvs out from beneath it; in the shallow part of the back 

 wall may sometimes be observed a pair of large foramina; the 

 aperture is terminal and large, occupying the upper two-thirds 

 of the area, irregular in size and shape, but varying round a type 

 which is long, broad, and nearly rectangular, with rounded corners, 

 rather wider at the foot than the head and with a slight inflexion 

 of the sides ; at the head the outline often becomes indistinct ; 

 a fairly typical length of aperture would be '30--4 mm., and breadth 

 •25— "27 mm. 



Ocecia small, inconspicuous swellings at the head of the zooecium ; 



