Search results
Results from the WOW.Com Content Network
These shells have 10 or 11 whorls and thus a very long suture, with an unusual sculpture of regularly placed papules along the suture itself. Nearly all snail shells (except for the shells of limpets , abalone , sea hares , etc.) can be visualized as a tube of increasing diameter, closed at the small end, and spirally wrapped around a central axis.
The four principal regions of an insect body segment are the tergum or dorsal, sternum or ventral, and the two pleura or laterals. Hardened plates in the exoskeleton are called sclerites, which are subdivisions of the major regions – tergites, sternites, and pleurites, for respective regions tergum, sternum, and pleuron.
The external or ventral region refers to sutures along the lower (outer) edge of the shell, where the left and right suture lines meet. The external (or ventral) saddle, when present, lies directly on the lower midline of the shell. As a result, it is often called the median saddle. On suture diagrams the median saddle is supplied with an arrow ...
The ventral (from Latin venter 'belly') surface refers to the front, or lower side, of an organism. [38] For example, in a fish, the pectoral fins are dorsal to the anal fin, but ventral to the dorsal fin. The terms are used in other contexts; for example dorsal and ventral gun turrets on a bomber aircraft.
Brachiopods have two valves (shell sections), which cover the dorsal (top) and ventral (bottom) surface of the animal, unlike bivalve molluscs whose shells cover the lateral surfaces (sides). The valves are unequal in size and structure, with each having its own symmetrical form rather than the two being mirror images of each other.
The trunk of the body contains, from superior to inferior, the thoracic region encompassing the chest [1] the mammary region encompassing each breast; the sternal region encompassing the sternum; the abdominal region encompassing the stomach area; the umbilical region is located around the navel; the coxal region encompassing the lateral (side ...
Anatomical "lines", or "reference lines," are theoretical lines drawn through anatomical structures and are used to describe anatomical location. The following reference lines are identified in Terminologia Anatomica: Anterior median line; Lateral sternal line: A vertical line corresponding to the lateral margin of the sternum.
In most fossil nautiluses, the siphuncle runs more or less through the center of each chamber, but in ammonites and belemnites it usually runs along the ventral edge of the shell. In some fossil straight shelled nautiloids, cylindrical calcareous growths ("siphuncular deposits") around the siphuncle can be seen towards the apex of the shell.