44 



M.K. HOWARTH 



1958b Glochiceras (Lingulaticeras) pseudocarachteis (Favre); 

 Ziegler: 144, figs 55, 56; pi. 14, figs 1 1-13. 



Material. Four specimens, C A7 1 7-20, from the Breadloaf Con- 

 cretions in the Kilya Member, east side of Wadi Arus. 



Description. The largest specimen is complete up to its partly 

 intact mouth-border at 22. 1 mm diameter; the mouth-border is flared 

 at the ventral rostrum and is preserved near the umbilicus, but it is 

 missing at the middle of the whorl side, so lappets are not preserved 

 and it is not certain that the specimen is adult, though the umbilical 

 seam uncoils slightly; the body-chamber is exactly half a whorl 

 long. The three others are smaller immature specimens of 17-19 mm 

 diameter; two have slightly more than half a whorl of body-chamber 

 ending in a broken aperture, with the mouth-borders just missing, 

 while the third has one-sixth of a whorl of body chamber. The whorl 

 section is ellipfical with only a slight flattening on the venter. 

 Flexuous radial striae of low relief bend backwards at the middle of 

 the whorl side, then curve forwards and cross the venter; they 

 increase in relief to form low curving ribs on the venter of the body- 

 chamber of the largest specimen. 



Measurements 









D 



Wh 



Wb 



U 



CA717 21.3 



9.5 (0.45) 



6.3 (0.30) 



5.4 (0.26) 



CA720 16.2 



7.9 (0.49) 



5.2 (0.32) 



3.9 (0.24) 



CA719 15.6 



7.1 (0.46) 



4.7 (0.30) 



4.1 (0.26) 



Remarks. These four small specimens match Ziegler's (1958b) 

 redescription and figures of Favre's species exactly, and in particular 

 the size of the umbilicus (24-26% of the diameter) is correct for this 

 species. The similar G. (L. ) modestum Ziegler ( 1958b: 1 39, figs 52, 

 53; pi. 14, figs 3-5) has stronger ornament on the side of the whorl 

 and a larger umbilicus. G. (L.) pseudocarachteis occurs in the 

 Beckeri and Hybonotum Zones in southern Germany and France. 



Occurrence. The lower marly part of the Kilya Member, Naifa 

 Formation, east side of Wadi Arus; Beckeri Zone, Upper 

 Kimmeridgian. 



Superfamily STEPHANOCERATACEAE Neumayr, 1875 



Family SPHAEROCERATIDAE Buckman, 1920 



Subfamily MAYAITINAE Spath, 1928 



The presence of Mayaitinids is important in fixing the date of the 

 basal part of the Billum Member as no younger than Upper Oxfordian. 

 Of the five specimens found, two are compressed, involute frag- 

 ments of fine-ribbed Epimayaites; the other three are more evolute 

 body-chambers with strong biplicate ribs, here identified as 

 Paryphoceras: they might be macroconchs and microconchs respec- 

 tively. As common ammonites in the East African - Indian Ocean 

 area, the last Mayaifinids are not younger than the top of the 

 Oxfordian. 



Gqwus EPIMAYAITES Spath, 1928 

 Type species. Stephanoceras tmnsiens Wsiagcn, 1875. 



Epimayaites sp. indet. 



PI. 3, fig. 2 



Material. Two fragmentary specimens, CA 1085-86, from the 

 basal 5 m of the Billum Member, Naifa Formation, Bimammatum 

 Zone, Upper Oxfordian, 1 km east of the AI Ma'abir road/river 

 crossing. 



Description. One is a fragment of a whorl of approximately 1 30 

 mm diameter attached to nearly half of a partly crushed inner whorl; 

 the other is a half whorl fragment of about 80 mm diameter. The 

 whorls are involute, have a small umbilicus, and a rounded, com- 

 pressed whorl section. Fine ribs on the outer half of the whorl are 

 projected forwards on the venter; the inner half of the sides of the 

 whorls are almost smooth. Both are too fragmentary for specific 

 identification. 



Genus PARYPHOCERAS Spath, 1928 



Type species. Paryphoceras badiense Spath, 1928 (p. 224), by 

 original designation (Spath, 1928: 247). 



Synonym. Prograyiceras Spath, 1928; type species, Dhosaites 

 grayi Spath, 1 924a. 



Remarks. These are smaller, more evolute Mayaitinids than 

 Maycdtes itself or Epimayaites, and are strongly ribbed to the end of 

 growth. They are probably microconchs corresponding to the much 

 larger sphaeroidal macroconchs of Mayaites and Epimayaites. Apart 

 from the slightly denser ribbing of P. badiense. there are no differ- 

 ences between the type species of Paryphoceras and Prograyiceras, 

 which are here put into synonymy, and Paryphoceras is chosen as 

 the name for the group. 



Paryphoceras grayi (Spath, 1924a) PI. 3, fig. 9 



1875 Stephanoceras nepalense (Grey); Waagen: 136, pi. 35, fig. 

 2. 

 71875 Stephanoceras fissum (J. de C. Sowerby); Waagen: pi. 36, 

 fig. 4. 

 1924a Dhosaites grayi Spath: 10 (nom. nov. for Waagen, 1875: 

 136, pi. 35, fig. 2). 

 71928 Paryphoceras stephanoides Spath: 248 (nom. nov. for 

 Waagen, 1875: pi. 36, fig. 4). 

 1928 Prograyiceras grayi (Spath); Spath: 250. 

 1928 Prograyiceras tramaimense Spath: 251, pi. 28, fig. 7; pi. 

 50, fig. 5. 

 71931 Prograyiceras cocosiforme Spath: pi. 1 15, fig. 1. 



Material. Two specimens from the basal 8 m of the Billum 

 Member: one, CA1087, from 1 km east of the Al Ma'abir road 

 crossing, the other, CA822, from the western end of Jebel Billum. In 

 addition, a photograph was taken of the external mould of a speci- 

 men on a large slab of limestone 7-8 m above the base of the Billum 

 Member at the Perisphinctid Cliff in eastern Jebel Billum. 



Description. All specimens are laterally flattened body-cham- 

 bers of 100-110 mm diameter maximum size. One is about 240° 

 long and might be a nearly complete microconch. The whorls are 

 involute, though the umbilicus is moderately wide, and the umbilical 

 seam may be 'uncoiling' in the near-complete specimen (PI. 3, fig. 

 9). Strong radial primary ribs bifurcate at, or just before, the middle 

 of the side of the whorl, giving rise to equally strong secondaries 

 which bend slightly forwards in crossing the venter. There are a few 

 extra intercalated secondaries, and the ratio secondaries/primaries is 

 2.1/1. 



Remarks. This is the most coarsely ribbed species of 

 Paryphoceras. represented by several specimens figured by Waagen 

 and Spath, which the Yemeni examples resemble closely. It is 

 difficult to be certain whether the small evolute holotype (Waagen, 

 1875: pi. 36, fig. 4) of P. stephanoides Spath really belongs to this 

 species, but it may be a small microconch, adult at 65-70 mm 



