268 - CRETACEOUS PELECYPODA 



4. Galeomma^ Turton, 1825. Elongately oval, sub-equilateral, with a large 

 gape in front, somewhat pearly, with decussate striae on the surface; cartilage 

 internal under the beaks, with no teeth in the hinge in the type species, (?. Turtoni, 

 Sowerby C=? Tellina aperta, Penier). Deshayes (Proc. Zqol. Soc, Lond., 

 1855, p. 167), however, describes a great number of species which he refers to 

 Oaleomma, though they have distinct cardinal teeth or rather, as he says, an arti- 

 culated hinge. Whether these have to be separated in a distinct genus, as appears 

 probable, or whether the characters of Galeomma have to be changed in so far as 

 the hinge-teeth were sometimes obsolete and at other times developed, can only be 

 determined by a re-examination of the materials. Deshayes considers the species 

 with hinge-teeth as a mere section of Galeomma. 



5. Thyreopsis, H. Ad., 1868, (Proc. Zool. Soc, Lond., p. 14). Shell resem- 

 bling Galeomma, nearly equilateral, sub-triangular, beaks slightly tumescent and 

 with the whole of the ventral margins widely gaping; type, Th, coraliophaga, 

 H. Ad., from Mauritius. I have received from Bombay through the Pev. 

 Mr. Eairbank an apparently new species of the same genus. The specimens do 

 not show any siphons externally^ but these may have been retracted before the 

 animals were placed in spirit. I shall take an early opportunity to note their 

 anatomical peculiarities. 



XXVII. Family— SO LBMYIJD^. 



The animal of Solemya is characterized by its elongated form, a wide anterior 

 gape for the protrusion of the foot, reaching to near or beyond the middle of the 

 ventral side; a single posterior exhalant short siphon, a pair of thick fleshy gills 

 on either side, and four narrow, falciform palps at the mouth ; the foot is large, 

 deeply grooved, or excavated below, expansible, and provided with a fringed edge. 



The shell is peculiar by its elongated, solenoid form, gaping valves which are 

 of a thin structure, nearly obsolete hinge-teeth, strong ligament, being partially 

 internal and partially extending over the hinge region, and by an entire pallial line. 



According to these general characters of the animal and shell, the genus Solemya 

 undoubtedly exhibits the greatest relation to Galeomma, next to which it must 

 naturally be classified. 



Pecluz, in his account of the anatomy of Solemya (Journ. de Conch., 1862, 

 vol. X, p. 110,) enters in detail into its comparison with that of Solen, though he 

 does not add many new facts beyond what we already find introduced into concho- 

 logical works. He states that there are two openings posteriorly, the one, upper or 

 exhalant, probably prolonged into a short siphon, the other is closed by a lamina. 

 Is it then an opening at all, corresponding to the inhalant or branchial siphon, or is 

 it not? It is impossible to answer the question from Pecluz 's account. Com- 

 paring the animal of Solemya with that of Galeomma, I rather think it probable 

 that there is no other but the exhalant opening. 



There are only five recent species of Solemya known from the present seas ; 

 fossil species, however, sparingly occur from the oldest formation upwards. I 

 have here associated with this genus a great number of fossil, mostly palaeozoic 



