104 



A.B. SMITH ETAL. 



less uniserial to peristome, with no pore crowding whatsoever. Small 

 buccal pores are present at the peristomial margin. Periproct oval, 

 longitudinal, in distinct anal sulcus opening closer to the posterior 

 margin than the apical system. 



Occurrence. Maastrichtian, horizon 2 (top) and 4, Santander; 

 Maastrichtian, horizon 6, Olazagutia Pass, Navarra province. This 

 species also occurs in the upper Lower to lower Upper Maastrichtian 

 of the Maastricht district. The Netherlands and Belgium (Van der 

 Ham et al., 1987), the Maastrichtian 'Craie phosphatee" at Ciply, 

 Belgium (Lambert, 1898b) and the Maastrichtian at Fresville, 

 Manche, France (Lambert collection). 



Material studied. BMNH EE4403, EE6148-49, MGB 37519. 



Remarks. This is a small species of juvenile appearance (simple 

 short petals, simple phyllodes, absence of bourrelets). There are 

 several names available for such forms, but they lack distinctive 

 characters and are virtually impossible to separate. Consequently, 

 we group all together here under the name A^. coravium Defrance. 

 This species is readily distinguished from the co-occurring A'. 

 scrobiculatus by its shape, which is much less tumid and with a 

 deeply sunken oral surface, and by its phyllodes, which are com- 

 pletely undifferentiated. It differs from A', geayi in having a more 

 posterior periproctal opening. 



Nucleopygus scrobiculatus (Goldfuss, 1829) 



PI. 4, figs 1-6; Fig. 12 



1829 Nucleolites scrobiculatus Goldfuss: 138, pi. 43, fig. 3. 

 1935 Lvchnidius scrobiculatus (Goldfuss); Smiser: 49, pi. 4, fig. 



10. 

 1957 Nucleopygus scrobiculatus (Goldfuss); Engel & Meijer: 



88, pi. L 

 1 987 Nucleopygus scrobiculatus (Goldfuss); Van der Ham et al. : 



30, pi. 11, fig. 3. 



Diagnosis. Test up to 26 mm in length, ovate; width 85-90% of 

 length, widest centrally; height 60-65% of length, tallest behind 

 apical disc. Apical disc a little anterior of centre (40% of length); 

 tetrabasal with four gonopores. Petals subequal with almost parallel 

 columns. Periproct supraambital, but positioned far to the posterior 

 on the steeply sloping posterior face; longitudinal with anal sulcus 

 only pronounced in juveniles. Oral surface strongly pulvinate with 

 peristome deeply invaginated. Peristome transverse and rounded 

 pentagonal. Phyllodes hardly expanded adorally, with a single series 

 of pores, becoming offset close to the peristome in specimens up to 

 15 mm length; with one pore in each of the first two groups of three 

 insert in larger individuals. Peristome with deep tuberculate vesti- 

 bule leading into peristome; buccal pores near top of this vestibule. 

 No bourrelets. Narrow granular tubercle-free zone present posterior 

 to the peristome. 



Occurrence. Maastrichtian, horizon 4. Santander; Maastrichtian, 

 horizon 6, Olazagutia Pass, Navarra. 



Material studied. BMNH EE6 154-61, MGB 37458, 37517 



Remarks. We have slight reservations about uniting our material 

 with A', scrobiculatus. The holotype of N. scrobiculatus was estab- 

 Hshed for a 7 mm individual. Later additional specimens were 

 described by Engel & Meijer ( 1 957 ) and Van der Ham etal.{\9%l) 

 up to 21 mm in length. Small individuals from Santander and 

 Olazagutia correspond very closely with the Maastricht population. 

 However, larger specimens become progressively less similar, show- 

 ing a less pulvinate lower surface, more rostrate posterior and 

 phyllodes with more offset pores. When we consider the full range of 



• 1 1 



Fig. 12 Camera lucida drawing of plating in Nucleopygus scrobiculatus 

 (Goldfuss. 1829) from the coast west of Cabo Mayor (Santander. 

 Cantabria); BMNH EE6154. phyllodes and peristome margin. Scale bar 



sizes present at Santander, there is no clear-cut separafion between 

 the smaller and larger individuals. We therefore conclude that the 

 small differences are growth-related and that all our material belongs 

 to the same species. 



This species differs from N. coravium in having the periproct 

 positioned on the steeply sloping part of the test, much closer to the 

 posterior margin, in being much more pulvinate with a more rounded 

 ambitus, and in lacking a strong saggital depression on its oral 

 surface. 



Family CASSIDULIDAE Agassiz & Desor, 1847 

 Genus OOLOfFGL'S d'Orbigny, 1856 



Diagnosis. Elongate cassiduloids with flat base and subcentral, 

 pentagonal peristome surrounded by weak bourrelets, and widened 

 phyllodes comprising inner and outer series. Apical disc with three 

 gonopores, no gonopore present in anterior left portion of disc. 

 Petals rudimentary to poorly developed. Broad pitted tubercle-free 

 zone present both anterior and posterior to the peristome. 



Oolopygus sp. Fig. 13a 



Occurrence. Maastrichfian, horizon 5, Santander. 



Material studied. BMNHEE6169. 



Remarks. Our solitary specimen is a small individual just under 

 10 mm in length. It is too small to be identified with certainty to 

 species level, but has sufficient characters to be confident about its 

 generic identity. Specifically, it possesses only three large gonopores, 

 and the oral surface is flat with a small subcentral mouth. Bourrelets 

 are small but distinct, and a granular naked zone is developed on the 

 oral surface. It may be a juvenile individual of O. pyriformis 

 (Lamarck), the Maastrichtian species that is found in the Maastricht 

 area. However, at this size it also bears close resemblance to 

 Oolopygus rostriformis (Kadilnikova & Moskvin) from the 

 Palaeocene of Mangyshlak, Kazakhstan. 



Genus /?//FA^Cf/OFyGf/Sd'Orbigny, 1856 



Diagnosis. Small cassiduloids with a flat base and low domal 

 profile. Peristome small, subcentral, surrounded by weak bourrelets 



