On Cretaceous Cephalopoda from Zulidand. 227 



1913. Pachydiscus collujatns, Nowak. Unters. Cephal. ob. Kreide 

 Poleu, iii, Bull. Ac. Sci. Cracovie, ser. B, p. 361, pi. xliii, fig. 30, 

 pi. xliv, fig. 39. 



A completely septate specimen (No. 5489) of 145 ram. diameter has 

 an umbilicus of about 20 per cent, of the diameter and a whorl thickness 

 of about 60 per cent. The ribbing is obscure, the example being only 

 an internal cast ; but there are about 25 costae on the outer whorl, 

 weakened at the grooved siphonalline and with a slight forward sinus. 

 Some of these costae do not reach to the rounded umbilical border ; 

 those that do are not distinctly tuberculate, and the inner whorls, as 

 shown in the deep umbilicus, are almost unornamented. There are 

 only nine septa on the last whorl, but these attain an extreme degree 

 of complication, equalled, perhaps, only by such forms of Parapachy- 

 (//./'* as P. quiriquincue (Philippi), Steinmann sp. 



The specimen shows close resemblance with the examples figured by 

 Biukhorst on pi. viii a, and which were selected as typical by 

 Grossouvre, though Pervinquiere * was of opinion that the large 

 form figured by Binkhorst on pi. viii, and which was renamed 

 P. van den broecJci, should be taken as type of Binkhorst's species, f 



The present example differs from the typical P. coHigatus (pi. iv, 

 fig. 3, and pi. v, fig. 1, in G-rossouvre) only in having, at a radius of 

 75 mm., a thickness of 75 mm., not 52 mm. as given by Grossouvre: 

 in other words it retains the globosity of the inner whorls of 

 P. collujatiix to a larger diameter. The costation, possibly, also is a 

 little too distant in the Zululand example. 



One of Schliiter's j examples of Parapachydiscu'S witteJdndi has 

 this more distant costation and thick whorls, but judging by a 

 number of Westphalian examples of this species in the British 

 Museum, the wide and strongly costate umbilicus separates Schliiter's 

 species from the form here described. 



Para i>a <-li inl^r a x '? portlocki, Sharpe sp., similarly differs from the 

 latter in having a wider umbilicus, surrounded by tubercles. In 

 whorl-shape, however (thickness -.- 60 per cent, of the diameter), the 



* "Et, de Pal. Tunis," I, " CY-ph. d. Ter. Sec.," 'Carte Geol. d. 1. Tunisia' 

 (1907), p. 175 (footnote). 



t This "species" was withdrawn in 190S by A. de Grossouvre, who then 

 figured Binkhorst's original (in the Berlin Museum) a poorly preserved exam pie. 



t ' Ceph. d. Ob. Deutsch. Kreide./ I, Palaeontogr., vol. xxi (LS72), c. g. example 

 2 of p. 68 (A. robustus), with thickness = 57 per cent, of the diameter, pi. xxi, 

 figs. 5 and (5 ; pt. ii (1870), p. 160. Boule, Lemoine and Thevenin (loc. cit., II, 

 1907, p. 22) wrongly consider this species of Parapachydistus to be the type of 

 Pachydiscus, Zittel. 



"The Fossil . . . Mollusca . . . Chalk of England," II, 'Ceph.,' 

 Pal. Soc, Mon., 1854., p. 30, pi. xiii, figs. 2, 3. 



