24, CRETACEOUS PELECYPODA 



III. MAllTESIA, Leach, 1821, (see p. 20). 

 1. Mabtesia tundens, StoUczka, PI. II, Pigs. 5-6. 



3Iart. testa cuneiformi, antice suUnJlala ac rotundata, postice attemiata et ad 

 terminationem subtruncata ; hiatu antico awjusto ; superficie in area centrali subtile 

 striata, sulco mediano ab umbonibus decurrcnte divisa ; reffione poslica luteraliter 

 minute riigosa, area iwstica supra subcariiiata ; impressione vmsculari i^ostica valde 

 elongata; valvula accessa umbonali parva, late ovata, antice emarginata ; marginibus 

 valvarnm ante umbones elevatis ac rejlexis. 



The short, anteriorly inflated and globular form of this shell easily distinguishes 

 it from other known species. Young specimens (fig. 5) are more regularly club- 

 shaped, the attenuation of the valves from the front towards the posterior end being 

 more gradual than in old ones. The valves have a distinct, though very narrow 

 opening in front for the protrusion of the foot, the sheUy covering being somewhat 

 prominent ; the surface of the central area is finely striated, and the striae pass over 

 the median groove almost continuously ; the posterior area is very slightly rugose. 

 The accessory valve covering the umljones is thin and anteriorly emarginated ; it is 

 rather broadly oval, but I have not been able to trace exactly its posterior margin. 

 Locality.— M-OxaNidiioov; boring in wood together with the next species. 

 Formation.— Ooiaioov group. 



IV. PAEAPHOLAS, Conrad, 1848, (see p. 20). 

 1. Parapholas mersa, StoUczka, PI. II, Pig. 7. 



Paraph, testa elongata, ctmeiformi, antice rotundata, subinjlata, postice regula- 

 riter attenuata ; hiatu antico minimo ; superficie lateraliter minute striata, postice 

 supra lamellose riigosa; area centrali dnobus szilcis approximatis ab umbonibus 

 ad peripheriam decttrrentibus notata ; valvulis accessis supira umbones sitis inter se 

 contingentibus, semicircidaribus ; valvula dorsali jiostumbonali stiliformi, simplici ; 

 ventrali similariter constructa, sed longitudinaliter bipartita. 



This is a typical species of Parapholas, having the umbonal accessqiy valve 

 divided lono-itudinally, but in every other respect the shell resembles a Martesia. 

 The two furrows running from the umbones towards the periphery are said to be 

 present in all known species of Parapholas ; there are, however, some species of 

 Martesia known {M. branchiata, Gld., and others) which also possess two umbonal 

 valves. On the other hand, there occurs a species in the Irawadi delta, described by 

 Mr. W. Blanford as Martesia fliiminalis, (Journ. Asiat. Soc, Bengal, vol. xxxvi, 

 1867 p. 67, pi. 3, figs. 1-3), which has a divided umbonal accessoiy valve, but only 

 one rib running from the umbones to the periphery, a second one being only internally 

 and not very distinctly marked ; it is almost parallel to the superior margins of the 

 valves. Still the species must be considered as a Parapholas and not as a Martesia, 

 though I must again say that the distinction scarcely deserves to be regarded as 

 of generic value. 



