1. Arms and web
   1. Web attaches to ventral margin of arm to somewhat over half of the arm length; attachment to dorsal margin unknown due to damage.
   2. Single web nodule present at distal point of attachment of web to ventral arm margin. This occurs opposite about sucker number 25.
   

   Figure. Portion of arm III showing web nodule on ventral margin of arm. Drawing from Hoyle, 1904.

   3. Arm suckers number over 50 (distal 5-10 mm missing).
   4. First cirri begin between suckers 4 and 5.
      
      
2. Shell
   1. "Horseshoe-shaped", smooth surface with no "characteristic markings or prominences."
   

   Figure. The shell of G. hippocrepium. Left - Lateral-oblique view of shell. Right - Dorsal view of the body showing the position of the shell and one fin. Drawings from Hoyle, 1904.

3. Measurements
   • Total length - ca. 80 mm.
   • End of body to mantle margin - 23 mm.
   • Width of body - 20 mm.
   • Width of head - 22 mm.
   • Length of fin - 28 mm.
   • Width of fin at origin - 13 mm.
   • Diameter of largest sucker - 1.2 mm.
   • Arm I: Right - 80,; Left - 90,.
   • Arm II: Right - 75,; Left - 85,.
   • Arm III: Right - 70,; Left - 85,.
   • Arm IV: Right - 65,; Left - 75,.

Comments

The above description was taken from Hoyle (1904). Hoyle gave few characters of specific value in his original description. Voss and Pearcy (1990) state that the type is in poor condition and little can be learned from it. However they did not declare G. hippocrepium a nomen dubium.

Among Pacific species, G. hippocrepium differs from:

• G. abyssicola by, possibly, the sucker number at the web nodule (25 vs 33) and non-lobelike wings on the shell.
• G. bathynectes by no clear characters other than locality.
• G. innominata in having no median ridge on the outer surface of the shell saddle, a shell without shoulder blades or expanded wings.
• G. meangensis in having a shell without shoulder blades.
• G. pacifica by no clear characters other than locality.
• G. tuftsi in having no transverse groove on the external surface of the shell saddle and no shell shoulder blades.