. Bulletin of the British Museum (Natural History), Geology. AMMONITES OF THE ENGLISH CHALK ROCK 3 1 3 Occurrence. Rare in the Chalk Rock, of Hertfordshire and Oxfordshire, in the H. planus Zone of ? Kent and Sussex and in the Upper Turonian of Sardal, Sweden. Genus PSEUDOJACOBITES Spath, 1922 [Pseudopuzosia Spath, 1926; Rotalinites Shimizu, 1935] Type species. Pachydiscus farmeryi Crick, 1910. Moderately evolute, inflated with strong constrictions, behind each of which is a strong rounded rib springing from an umbilical bulla, and weak irregular intermediate ribs. On the outer whorls there ar
. Bulletin of the British Museum (Natural History), Geology. AMMONITES OF THE ENGLISH CHALK ROCK 3 1 3 Occurrence. Rare in the Chalk Rock, of Hertfordshire and Oxfordshire, in the H. planus Zone of ? Kent and Sussex and in the Upper Turonian of Sardal, Sweden. Genus PSEUDOJACOBITES Spath, 1922 [Pseudopuzosia Spath, 1926; Rotalinites Shimizu, 1935] Type species. Pachydiscus farmeryi Crick, 1910. Moderately evolute, inflated with strong constrictions, behind each of which is a strong rounded rib springing from an umbilical bulla, and weak irregular intermediate ribs. On the outer whorls there are strong ventrolateral and siphonal tubercles. The sutures interlock to a slight extent and have long narrow highly-divided bifid saddles and trifid lobes (Fig. 2).. Fig. 2 Suture ot Pseudojacobites farmeryi (Crick), x 2. Study of two well-preserved specimens collected in recent years has surprisingly demonstrated that the holotype of Desmoceras marlowense Noble, the type species of Pseudopuzosia Spath, consists of the inner whorls of a specimen of Pachydiscus farmeryi Crick, the type species of Pseudojacobites Spath. The genus is readily distinguished from Lewesiceras not only by the ventrolateral and siphonal tubercles on the outer whorls but also by the more depressed whorl section, straighter ribs and constrictions and the interlocking sutures with longer and narrower elements (cf. Fig. 2 and PI. 5, fig. 1). The tubercles and the weaker, less regular ribbing distinguish Pseudojacobites from Tongoboryoceras. Pseudojacobites ranges from Upper Turonian to Coniacian. The Santonian attribution of a species from Texas is doubtful. The genus is widespread but apparently always rare, occurring in Madagascar, southern India, Japan and Texas as well as England. Pseudojacobites farmeryi (Crick) Fig. 2; PI. 4, fig. 5; PI. 5, fig. 1; PI. 6, figs 2, 3 1910 Pachydiscus farmeryi Crick : 345; pi. 27, figs 1, 2. 1911 Desmoceras marlowense Noble : 398, text-figs 1, 2. 1922 Pseudojacobites far
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