VENUS. 



several on our own shores. Many of them are very briF- 

 liantly coloured internally, one is remarkable for the 

 orange colour of its teeth, another for a deep violet 

 coloured stain, and another is of a fine orange colour; 

 the lamellated and cancellated external surface of others 

 is very beautiful. We have lately seen a most singular 

 species in which the lunule forms a deep hollow depres- 

 sion as in the Cardium retusum, found at Madeira by the 

 Rev. R. T. Lowe : this together with another nearly glo- 

 bular species (the Venus rugosa ) shows a fourth tooth in 

 one valve placed just beneath the lunule, and fitting into 

 a corresponding hollow in the other valve, in this respect, 

 though not otherwise approximating to Cytherea. Other 

 species show slight differences in the shape and position 

 of the teeth, and one, the V. mercenaria, has an elongated 

 rough space behind the teeth and just below the fulcrum 

 to which the ligament is attached. The last mentioned 

 species has received its name (Venus mercenaria) from the 

 circumstance of its being used as money, under the name 

 of Wampum by the North American Indians. 



In general form the Veneres may be described as 

 orbicular or somewhat ovate, they are usually rounded at 

 both ends, seldom slightly acuminated posteriorly. They 

 are usually rough externally, with concentric lamellae, 

 and in general more or less cancellated. The beaks are 

 prominent, and there is mostly a heart-shaped impression 

 just below them. The teeth, as we have shown above, 

 are variable, there are however three diverging teeth in 

 each valve. Two muscular impressions which are lateral, 

 distant, and somewhat orbicular are united by a pallial 

 impression, which has for the most part a small sinus 

 posteriorly. The ligament is external, though sometimes 

 nearly hidden by the outer edge of the shell extending 

 beyond it and almost covering it. 



Fossils of this Genus do not appear to abound, thoughr 

 they are not very uncommon ; they belong principally to 

 the tertiary beds. 



We have represented one species of each of the^ 

 divisions named above. 



