. Bulletin of the British Museum (Natural History), Geology. CRETACEOUS AMMONITES AND NAUTILOIDS FROM ANGOLA 369 and reduced to striae on the ventral half, then (unlike the ribs of B. anceps) they increase in strength again and bend slightly back to pass over the rounded venter as prominent crenulations; there are between 2 and 3 times as many such ribs crossing the venter as there are arcuate ribs on the side. The ribs are also reduced to striae across the dorsum and are projected only slightly forwards. All the specimens bear such ribs except the single largest one which is nearly smooth. Th
. Bulletin of the British Museum (Natural History), Geology. CRETACEOUS AMMONITES AND NAUTILOIDS FROM ANGOLA 369 and reduced to striae on the ventral half, then (unlike the ribs of B. anceps) they increase in strength again and bend slightly back to pass over the rounded venter as prominent crenulations; there are between 2 and 3 times as many such ribs crossing the venter as there are arcuate ribs on the side. The ribs are also reduced to striae across the dorsum and are projected only slightly forwards. All the specimens bear such ribs except the single largest one which is nearly smooth. There are no constrictions. Remarks. Haughton (1928: 278) had "numerous examples" of this species and figured three of them. A holotype was not designated, so the whole collection consists of syntypes and a lectotype designation can be made. The original of Haughton's pi. 14, fig. 6 is lost or not available for study, and as this figure does not show any of the ornament it is not suitable to be a lectotype. The specimen from which Haughton obtained the cross section of his pi. 14, fig. 8 (refigured here PI. 7, fig. 1) is a very large smooth body chamber fragment, with shallow ventral grooves peculiar to its large size, and is also unsuitable for a lectotype. The lectotype designated is therefore the medium-sized specimen figured in PL 6, fig. 6, which is half septate, half body chamber, and shows the ornament weU. It is one of the best preserved syntypes. Two further specimens are figured (PL 5, fig. 3; PL 6, fig. 7; Text-figs. 13, 15) which show the ornament and cross section at different sizes. Little variation in the ornament can be detected in the 15 specimens, for all the medium-sized examples are ribbed and the two largest body chambers become nearly smooth. The venter is smoothly rounded in all cases with no trace of sharpening or of a Figs. 5-15. Cross sections of specimens of Baculites figured in the plates. For details of individual specimens see plate
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