175 



1. agglutinans, Desk. 



2. apertissima, id. 



3. brevis, Sow. 



4. cucullata, Desk. 



5. denticulata, id. 



6. difficilis, id. 



7. dubia, Penn. 



8. grandis, Desk. 



9. kians, Ckemn. 

 10. lnunilis, Desk. 



Species. 



11. hyalina, £cw. 



12. irnpressa, Desk. 



13. indistincta, id. 



14. interrupta, &?. 



15. intersecta, id. 



16. laevigata, ii. 



17. lamellosa, id. 



18. macrochisma, id. 



19. mumia, Speng. 



20. mytiloides, Z«m. 



21. ovata, #cw. 



22. Philippinensis, Desk. 



23. plicatilis, id. 



24. pupina, i<#. 



25. rostrata, Speng. 



26. rugulosa, /So?#. 



27. Riippellii, Desk. 



28. spathulata, id. 



29. tenera, ^. 



30. truncata, Sow. 



Figures. 



Gastroch^na ovata. PL 45. Fig. 240. Shell, taken from its crypt 

 and placed on its ventral edge to show the anterior gape and posterior 

 external ligament. 



Gastrochjsna {Fistxdana) mumia. PI. 46. Pig. 246. Shell, with the 

 valves open, as contained within the club end of the tube. The 

 tube above shows the form of it before being broken to extract the 

 valves. 



Genus 3. CLAVAGELLA, Lamarck. 



Animal ; mantle closed in front except a minute slit for the pas- 

 sage of a small rudimentary foot ; edges of the mantle some- 

 times furnished with small tentacular processes corresponding 

 with tubular processes of the shell ; siphons united and extended, 

 the branchial siphon having the branchia continued into it. 



Shell ; ovate or oblong ovate, irregular, sometimes rudimentary ; 

 left valve fixed to the wall of the burrow, right valve free; 

 sheath variously elongated, subcylindrical, expanded at the top 

 like a flower, sometimes encircled with a 'frill or succession of 

 frills, lower end of the sheath enclosing the shell terminating 

 with a rudely shaped disk, having a minute central fissure, and 

 bordered by irregular spine-like tubes. 



Clavagella presents an interesting intermediate link between Gastro- 

 chana and Aspergillum ; but there is no great difference in the animal be- 

 yond the modifications of organs leading to a change in the construction 



