138 FIELD CoLuMBIAN MusEuM—GEOLOGY, VOL. II. 
slender ribs are spread outwardly, and were not doubled up below the 
wing bones. They cannot be ventral ribs, since these are large and broad 
in this species of Rhamphorhynchus, according to Zittel. 
In Prerodactylus spectabtlis, as figured in the books, a number of very 
delicate abdominal ribs are shown, as depicted by Von Meyer. ‘ An die 
unteren Halfte des Rumpfes kommen funf fadenformige Abdominalrip- 
pen. Sie sind fadenférmige, ohne sich gegen die Mitte her zu verstarken, 
und bei ihre Lange und diinnen Beschaffenheit etwas verbogen. Die erste 
Rippe, die langste, ergiebt 0.026.”* Is it possible that the abdominal 
and vertebral ribs have been confused in this description? 
Ventral ribs or parasternum. Pl. XLI, Fig. 2. The ventral ribs were, 
for the most part, lying in position nearly contiguous with the xiphisternal 
process. There appear to be four pairs, the first three lying together and 
united. The first pair is somewhat uncertainly shown, broken on the left 
side and partly concealed on the right below the border of the sternum. 
The second pair is very distinct. ‘They are somewhat V-shaped, co-ossified 
and thickened in the middle, and terminating outwardly in a slender 
point. The third pair was in position, co-ossified with the margins of the 
second pair, but not united in the middle. Another pair is seen by the right 
side of the tenth vertebra, partly beneath the ulna; their whole form can- 
not be made out, but they are wider and longer, apparently, than the third 
pair, to which they could have had no ossific union. ‘These ribs are all 
thin. In the restoration it seems evident that the last pair of these ribs 
would approach, if not actually meet at their ends, the anterior ends of 
the prepubic processes. I am very much inclined to believe that the 
prepubis is really not a part of the pelvis, but rather a part of the para- 
sternal ossifications. 
One of the best descriptions extant of the ribs of pterodactyls is that 
of von Ammon (op. ct.): 
“Die hintersten dreizehnte Rippe stellt einen zarten Knochenstreifen 
vor. Das untere Ende der Rippen ist verdickt und bildet ein kleines 
Gelenkképfchen, an welchem der obertste Theil einer Giirtelrippe der 
Bauchwand befestigt ist... . Durch ihre Verbindungen [d. h. der 
Abdominalrippen] mit den oberen Rippen bestehen also vollstandige 
Giirtel in der Bauchwand. Es schliessen sich immer zwei Bauchrippen zu 
einem formlichen Halbkreis zusammen. Am Vereiningungspunkte ist 
eine mediane Verdickung vorhanden, die eine nach unten Spitz auslau- 
fendes langes Képfchen bildet.” The ventral ribs of this pterodactyl 
(Rhamphorhynchus longicaudatus) are very thin and simple, in contrast 
with the broad ventral ribs of the larger forms of ARhamphorhynchus, 
according to Zittel. 
* Paleontographica, vol. x, p. 4, 1868. 
