Cephalopod Shell Terminology

[cngodles]

I found a key to figure out a species of Solenochilus, and I would like to attempt to create a visual guide of the differences in the key. Usually it's a A/B situation. While it's clearly written, I'm still having some trouble figuring out what the difference is.

 

So to start:

 

• Suture with ventral saddle.
• Suture with ventral lobe.

 

I've found this, but it seems like this type of suture has both:

 

 

Solenochilus has an exposed siphuncle, so the middle (venter) suture is usually interrupted by this. It's also usually straight. I have another 11-14 measurements aside from this first one.

 

Help

 

Update: This is the entire guide for those curious: https://docs.google.com/document/d/1hvqE3_MH0ke0XKCPgL2YeOaddCsIEOU5uOQyZxypCqU/edit?usp=sharing