10 



Genus 2. SILIQUARIA. 



Animal ; head distinct, having two small tentacles with eyes at 

 their bases ; branchice consisting of simple filaments placed be- 

 neath the left lobe of the mantle, which is slit throughout. 



Shell ; tubular, irregularly loosely convoluted, having a slit through- 

 out, which is sometimes a little articulated. 



It was some time after the discovery of the molluscan character of Ver- 

 metus that the Lamarckian SiUquaria (Serpula anguina, Linn., and Ser- 

 pula muricata, Born) were found to be similarly organized. The shell of 

 SiUquaria, especially S. muricata, as may be seen by our figure, is of more 

 irregular, Serpula-like growth ; yet it has the molluscan type of a prede- 

 termined maturity, and the slit, which constitutes its principal generic 

 feature, as distinguished from Vermetus, is the homologue of the slit in 

 Fissurella and Emargimda and of the row of holes in Haliotis. It in 

 fact covers a corresponding fissure in the left lobe of the mantle, adapted 

 to the passage of the branchise, which in this mollusk take the form of 

 protruding filaments. 



SiUquaria ranges with Vermetus in the eastern hemisphere, but is more 

 limited in species. None have as yet been found on the American shores. 



Species. 



1 . anguina, Lamarck. 4. laevigata, Lam. 6. papillosa, Rees. 



2. australis, Qi/oi/. 5. muricata, Bing. 7. squamata, Blainv. 



3. lactea, Lam. 



Figure. 



Siliquaria muricata. PI. 23. Fig. 136. Shell, showing the slit, which 

 passes through its entire length, and may be observed towards the 

 apex to be partially articulated. 



Family 2. MACROSTOMATA. 



Shell ; only slightly convoluted, sometimes perforated with a row 

 of holes. 



The Lamarckian system of classification does not apply with accuracy to 

 this part of the series. The family Macrostomata, even with the changes 



