70 KELLIAD^. 



notes and figures of M. Deshayes, and M. Mittre, we are 

 enabled to present the details which will be found in the 

 descriptions of the several species. 



The family of Kelliada. is an assemblage of minute and 

 mostly fragile bivalves, presenting but few variations of 

 colour and sculpture. They are free, equivalve, often very 

 inequilateral shells, closed or gaping in front. The liga- 

 ment varies in position, but is commonly cardinal and in- 

 ternal : the dentition is still more variable, cardinal and 

 lateral teeth being present or absent according to the genus 

 or species ; sometimes both kinds are entirely wanting. 

 The internal surface always presents an entire pallial im- 

 pression and roundish muscular scars. 



The animals, so far as known, present characters of great 

 singularity. Unless in Galeomma, an abnormal form at 

 best, we find them distinguished by the remarkable fea- 

 ture of having only one siphonal opening, and that the anal 

 one, which is sometimes sessile, sometimes produced into a 

 tube, whilst in most, possibly in all instances, the mantle is 

 folded anteriorly into a canal or tube, which appears to be 

 subservient to branchial purposes. The degree of union of 

 the margins of the mantle is very variable. All have a 

 grooved foot, provided with a byssiferous organ, and capa- 

 ble of being used as a creeping disk. The branchial leaflets 

 appear to be always separate, and the labial palps de- 

 veloped. 



There would seem to be a considerable affinity between 

 the Kelliada and the Arcadce and Mytilida. This we see 

 indicated in the variations of siphonal arrangement and the 

 peculiar foot of the animals, whilst the shell of Galeomma 

 reminds us of some Arks, and that of Montacuta substriata 

 of Crenella. On the other hand, there are distinct relations 

 to the LucinidcE and Cycladidce. 



