Figure 1

The shell and mantle of juvenile H. asinina . A. Dorsal view of shell, anterior to the right. Tremata are indicated by an asterisk. The white arrowhead points to a ridge with orange and blue spots in an area of red background, the black arrowhead points to a ridge on a white background possessing orange spots only. Scale bar = 1 mm. B. Inner surface of the shell depicted in A, anterior to the left. At the shell margin, only the prismatic layer (pr) is visible, whereas the nacreous layer (na) is deposited more centrally. C. Dorsal surface of the animal dissected from the shell, anterior to the right. The mantle is divided into two parts, the right mantle lobe (rml) and the left mantle lobe (lml). The digestive gland (dg) is normally situated within the whorl of the shell.