96 



A.B. SMITH ETAL. 



Genus PHYMOSOMA Haime, //; d'Archiac & Haime, 1853 



Diagnosis. Test depressed with apical disc opening large and 

 peristome hardly invaginated. Pore-pairs forming short phyllodes 

 adorally and becoming biserial adapically. Primary tubercles rela- 

 tively coarse, occupying most of the interambulacral plate. Tubercles 

 imperforate and crenulate. 



Phymosoma granulosum (Goldfuss, 1829) PI. 2, figs 3, 4 



1829 Cidarites granulosus Goldfuss: 122, pi. 40, fig. 7. 



1865 Cyphosoma granulosum Cotteau, in Cotteau 1861a-67a: 



684, pi. 1 169. 

 1898b Gauthieria broeki Lambert: 152, pi. 4, figs 1-5. 



Diagnosis. Test 20-25 mm in diameter, depressed in profile with 

 rounded ambitus. Ambulacra with five-geminate plate compound- 

 ing; pore-pairs arranged in arcs on ambital plates but becoming 

 biserial towards the apex. Large primary tubercle on ambulacral 

 plates, separated by single band of granules on ambital plates. Short 

 phyllodes developed adorally. Interambulacral plates a little wider 

 than tall and dominated by a single large primary tubercle with a 

 large mamelon. Narrow adradial and interradial bands. Peristome 

 hardly invaginated. 



Occurrence. Maastrichtian, horizon 2, Santander. 



Material STUDIED. BMNHEE6127. 



Remarks. Distinguished from Diplotagma sp. by its relatively 

 coarse interambulacral tuberculation, the tubercles largely filling 

 each interambulacral plate. Distinguished from Acanthechinus sp. in 

 having its peristome hardly invaginated and in having obvious adoral 

 phyllodes. P. hexaporum is similar, but has more pore-pairs to each 

 ambital ambulacral plate (six or seven as opposed to five) and has 

 distinct secondary tubercles to the adradial side of primary tubercles 

 on ambital and supraambital plates. 



Phymosoma hexaporum Lambert, 1927 



PI. l,fig. 15; Fig. 7 



1927 Phymosoma hexoaporum Lambert: 35, pi. 2, figs 25-27. 



1928 Phymosoma hexaporum Lambert: 61. 



1992 Phymosoma hexaporum Gallemi: 80, fig. 24. 



Diagnosis. Test relatively large and depressed, up to about 40 mm 

 diameter (esfimated). Apical disc pentagonal, peristome slightly 

 sunken and small (about 12 mm, estimated). Ambulacral plates 

 occupied by single large primary tubercle; areoles confluent adorally 

 and just separated on ambital and aboral plates. Pore-pairs in arcs of 

 six on ambital and subambital plates and forming distinct phyllodes 

 adorally. Aboral pore-pairs presumably arranged biserially, as in the 

 type, although none of our specimens has a well-preserved upper 

 surface. Granulation rather sparse. Interambulacral plates distinctly 

 wider than tall with adradial and interradial granular zones. Small 

 secondary tubercles only very weakly differentiated adradially on 

 adoral and subambital plates, but better developed adapically. 



Occurrence. Maastrichtian, horizons 4 and ?7/8, Santander. 

 Campanian/Maastrichtian beds at Erice, Navarra. 



Material studied. MGB 37556. BMNH EE6126, EE4422, 

 7EE4416. 



Remarks. Distinguished from Diplotagma by its taller inter- 

 ambulacral plates and stouter primary tubercles, and by its uniserially 

 arranged pore-pairs on ambital plates. It differs from P. granulosum 



Fig. 7 Camera lucida drawing of plating in Phymosoma hexaporum 

 Lambert, 1927 from the coast west of Cabo Mayor (Santander, 

 Cantabria); MGB 37556, adoral part of an ambulacrum. Scale bar = 1 

 mm. 



in having wide zones of granulation and by having six or seven rather 

 than five pore-pairs to each ambital ambulacral plate. 



Genus ACANTHECHINUS Duncan & Sladen, 1882 



Diagnosis. Phymosomatid with pore-pairs arranged biserially 

 from the ambitus aborally. Peristome deeply invaginated and pore- 

 pairs arranged uniserially adorally without phyllodes; primary 

 ambulacral tubercles not crowded adorally. One large primary tuber- 

 cle to each interambulacral plate. 



Acanthechinus sp. 



PL l.figs 11, 12 



Diagnosis. Specimen between 25 and 28 mm diameter; height 9.3 

 mm; rounded in profile with ambitus a little below mid-height. 

 Apical disc moderately large; peristome smaller, strongly invagi- 

 nated. Ambulacra tapering adapically; pore-pairs uniserial below the 

 ambitus but biserial from the ambitus adapically. Six or seven pore- 

 pairs to an aboral plate, but five on ambital plates. Ambulacral plates 

 with single large primary tubercle; tubercles separated by a single 

 row of granules both perradially and within a single column. Tuber- 

 cles remain separated towards the peristome. Eleven interambulacral 

 plates in a column, each with a single primary tubercle. Plates wider 

 than tall and primary tubercles confluent on ambital and adoral 

 plates. A band of small secondary tubercles is developed along the 

 adradial plate margin on the oral surface. On plates just above the 

 ambitus, a distinctly enlarged secondary tubercle appears close to 

 the adradial margin. 



Occurrence. Maastrichtian, horizon 2, Santander. 



Material studied. BMNH EE6 128. 



Remarks. The deeply sunken peristome, and relatively small and 

 wide plates, distinguish this from the two Phymosoma species. It 

 resembles Diplotagma, but that species has shorter and wider 

 interambulacral plates, with wider and more granular interradial and 

 perradial bands. Furthermore, Acanthechinus has a deeply sunken 



