Tusk Shells (Scaphopoda)

The Scaphopoda, or tusk shells, are a basal form of mollusk which filter feed on detritus and foraminifera from the surface of soft sediments.  The muscular foot (1P) anchors the anterior end of the body in the sediment while the apical (narrow) end protrudes the surface.  Water is drawn into the mantle cavity, which has no gills, via the apical opening using cillia.  Food particles are sorted from sediment before a muscular contraction ejects  the water back out the same opening.  This diagram shows an adult laterally within its shell (1) and ventrally without a shell (2) where blue represents nervous tissue, red is blood vessels, green is gonad and yellow is the digestive system which is shown isolated in higher magnification (3).  Further illustrations show a detailed progression of development (4-11).

Bryozoans (Ectoprocts) & Entoprocts

This wall chart shows the colonial nature of the so called moss animals. Note the position of the anus on many of the adults as this feature is their namesake; those with the anus within the crown of tentacles are Entoprocta (ento – within; proct – anus) those with the anus outside of the crown of tentacles are Ectoprocta (ecto – outside; procta – anus).There is large debate about the relationships of the two groups Ectoprocta and Endoprocta.  There are many similarities in superficial structures and morphology, however these similarities often mask dissimilarities such as the feeding crown of tentacles (lophophore/lophophore-like structure) which operates in opposing directions between the two groups.  Molecular data suggests these two are distinct phyla however many skeptics still class them together within Bryozoa.